December 14, 2021

Complete Guide to Email Warm Up Tools (which Increase Sender Reputation)

The complete 2021 guide to email warm up tools on the market and the impact these solutions + best practices on sender reputation.

Complete Guide to Email Warm Up Tools (which Increase Sender Reputation)

Email Warm Up Tools (Increase Sender Reputation): intro

Email warm up tools are becoming a key aspect of the technology stack every B2B company uses, to maximize the effectiveness of the automation they have already built in the go-to-market process. Companies which have used marketing automation and sales engagement emails for years to be efficient and help their team generate leads over email, have noticed a clear change in recent times- open and reply rates are plateauing or even declining as they increase the volume of marketing emails sent.
The reason this trend has been occurring is due to email service providers becoming increasingly proficient at identifying and filtering marketing and sales emails out of the priority inbox and into spam / promotions and unfocused folders. If this happens, prospects who you email do not have a chance to open and read your message, as it’s outside the view of their main inbox:

(credit: Typeform spam folder GIF)

Reaching the primary inbox is undoubtedly becoming more challenging due to the popularity of using automated emails to generate leads; but, as with every marketing trend, the businesses which have the best process and technology powering them are still achieving ROI and sales success via email, as over 80% of businesses use email to both acquire and retain customers. While, Hubspot outlines average returns on emails as a channel are $42 for every $1 spent.

Businesses that are in the top 10% of corporate marketers focus on implementing technology and strategy so their emails land in the primary inbox. Therefore, we believe it’s safe to say the use of cold email isn’t going away by any means, however, you may need to update your approach to stay at the top when it comes to email success. We’ll provide a high-level overview of the technology and best practices being used to achieve these marketing results in 2022.

Table of Contents:

  1. Email Warm Up Tools (Do I need one yet? - Quick Test)
  2. Why do outreach emails go to spam?
  3. Is cold outreach still effective?
  4. Cold email success benchmarks?
  5. What is a good reply rate for sales emails?
  6. How can I improve my cold outreach?
  7. What is email domain reputation?
  8. How to check my domain reputation + Flaws in the current methods?
  9. How can I improve my email reputation?
  10. How does an email warm-up tool work?

Email Warm Up Tools (Do I need one yet? - Quick Test)

Do I need an email warm up service for cold emailing yet? The answer is: It Depends!

The Answer is, Yes, if the following points describe your email marketing / demand generation process correctly:

- You're actively sending emails to generate sales opportunities and leads. (if this isn’t the case you’re probably a little early)

- You’re emailing over 1,000 prospects per month. (or approaching that volume in the near future and need to be ready)

- You have implemented a marketing automation tool so you’re no longer manually sending email.

- You are confident about where you source your email contacts / lists for campaigns from and understand the target customer profile you're reaching out to.

- Outreach emails are part of a long term strategy which you use to generate opportunities for the sales team and you expect the volume of emails you send to increase over the next 12-months as your sales and marketing team grows. (you’re not trialling / testing cold email to see if it might work to help sales).

If you answered ‘no’, to one or more of those questions the chances are you’re not quite at the stage yet where you’ll see an exponential impact from an inbox placement platform. The reason for this is your strategy needs to be scaled to really see a tangible benefit from enhancing your inbox placement (we’d advise you to potentially re-visit inbox placement in 6-12 months once the basics of your outreach strategy are solid).
On the other hand, if you answered yes to all the above points, you’ll want to evaluate tools which can help your inbox placement, in order to stay ahead of the competition and make sure valuable prospects see your content rather than your outreach emails being placed in promotion folders. Spam emails account for almost 50% of all email traffic worldwide (and this is a conservative estimate). When you send multiple outbound emails every day, even to high-quality data with a low bounce rate, the quantity of engagement emails from your domain overall (meaning opens, clicks, replies) looks significantly lower as a percentage of emails sent compared to the average email user/domain who only sends emails to people they already know. Major Email Service Providers (ESPs), such as Microsoft and Google, monitor this data for your sending domain against their users to automatically decide what percentage of your emails should be delivered to the primary inbox and how many should be placed into the spam or unfocused folders where users rarely open emails. Therefore, domains that receive high to normal levels of engagement on their emails are placed in the primary inbox more often than domains that receive low levels of engagement. This can become a vicious cycle of declining open rates, as the email providers place your emails in spam more frequently you are likely to receive even less engagement and so on… 

Fortunately, the objective of inbox placement platforms is to both help you track these rates reliably and improve your sender reputation by increasing the engagement you receive on your domain through replies, opens and emails being marked as important or moved out of spam by networks of real business email accounts. Email warming services or inbox placement platforms cannot eliminate the problem of emails you send landing in spam full stop - but, they are part of a comprehensive strategy to ensure the engagement your emails receive is maximised. The adoption of this technology throughout 2020-2022 by market-leading brands is an indicator that businesses that take go-to-market seriously should select a vendor to work with long term to improve inbox placement. 

Why do outreach emails go to spam?

ESPs want to deliver exceptional customer experiences for their users. This means having the systems in place to identify and root out spam senders, preventing them from reaching a user’s priority inbox. To the frustration of many legitimate senders, algorithms developed by ESPs have a tendency to create “false positives”. These are legitimate emails mistakenly sent to spam.

To prevent your emails from being mistakenly flagged as spam by the algorithms, you need to show the email providers that you are a legitimate and trustworthy sender. This can be done by using an email warming tool alongside a great email strategy to raise and maintain a high sender reputation. Here are a few reasons why your outreach emails could be going to spam:

  • You’ve sent too many emails from one email account rather than spreading outreach activity across multiple email accounts. Which has raised the risk profile of your campaigns and made them look less human. (this point applies for cold emails/ campaigns sent through the email client)
  • You’ve used content / keywords and a structure which the filtering algorithms of the email providers are choosing to automatically filter into the unfocused folders.
  • The engagement rates on your campaigns over time have shown email providers that your emails are likely to be automated and should be filtered by decreasing your reputation score. 
  • The prospects who are receiving your emails have reacted negatively to your content and actually manually marked your email as spam inside their email client. (this usually occurs when your content or follow-up is too aggressive and can lead to accounts being suspended)
  • You have not implemented a technical setup on your email account to show email providers you are a trustworthy sender. (SPF, DMARC and DKIM)  

Before you start ramping up your email volume to maximise lead generation, you’ll want to make sure you can start to track and increase your sender reputation. Otherwise, you’ll find you’re receiving diminishing returns as you scale. With Allegrow you’ll have a platform to accurately track sender reputation, analyse changes in your score and use our technology to build a better sender reputation in the long term. This occurs as Allegrow can simulate interactions on your domain to increase engagement making your accounts look more human. While allowing you to consistently track + analyse your sender reputation with real-time data  and conduct tests on your content variations so they are optimised for inbox placement based on data from real email inboxes via our crowdsourced network. 

Is cold outreach still effective?

Cold email outreach can still be incredibly effective and is undoubtedly the primary mechanism that B2B organisations use to generate new sales opportunities. Fortunately, the barrier to accessing the automation technology and contact data required to get an outreach campaign rolling has never been lower. However, if you aim to unlock the attractive ROI that’s often associated with email outreach, due to the increase in popularity and competition inside prospects' inboxes, you’ll need to consider an inbox placement strategy. As this is now the primary factor that separates highly successful campaigns from average ones in the current market climate.

In fact, cold email works so well you can find some of the worlds largest brands using it and no shortage of success stories:

Example #1 - Google, the worlds largest email provider, lists in the first bullet point of the responsibilities of their SDR job description  ‘Generate business leads through a mixture of outbound calling and emailing’. (We think it’s safe to say if Google is using outbound email you should too as a credible strategy to get in front of decision-makers)

Example #2 -  Growthonics (who are an Allegrow customer), helped their client, City Pantry increase outbound leads by 160%, with cold email as a core component of their strategy. As well as this success story they have worked and used cold email on behalf of major brands like American Express and Spotify. 

Example #3 -’s customer Sales Transformation Group grew their monthly recurring revenue by 3x using the outbound capabilities of’s platform. (Incidentally, another customer of, Lux Sales Consulting, now uses Allegrow and increased their email open rates from 30-50% after implementing the Allegrow platform). 

Cold email success benchmarks?

Mailchimp has extensively researched open rates for email marketing campaigns and found that the variation can range from 15.22% to 28.46%. However, it is important to recognise that open rates can often vary depending on industry, the volume that you’re sending and most importantly the type of email you’re sending. Outreach has documented specifically for outbound sales cadences - for a successful sales sequence you’ll want to be above these benchmarks:

  • Email open rates of 27% or higher.
  • Response rates across the entire sequence of above 12%. 
  • Bounce rates of less than 2.8%. 
  • Opt-out / unsubscribe rates of less than 1.1%. 

It’s important to note that market leaders in their given industry should expect and target to be well above these benchmarks, and in order to achieve best in class email statistics, you’ll need to optimise your inbox placement, content and cadence structure.

What is a good reply rate for sales emails?

A response rate of anywhere between 15% and 20% is strong. To achieve this, you will likely need to extensively test your email copy to land a winning formula. We’d also strongly advise that once you reach a high response rate you can’t simply ‘set and forget’ the content (otherwise you’ll find your results are going to decline over time). We recommend you update the copy used on your live campaigns at least once every 60-days. Launching content tests inside an environment like Allegow can identify which keywords and email structure decisions are informing the filtering decisions email providers make on your content. After all, running campaigns without testing content for inbox placement would be like posting a blog without considering how search engines rank keywords. 

Hyper-personalisation is a key factor for improving your reply rates. Taking a cookie-cutter approach to cold emailing is a recipe for disaster (you’ll notice we’re not providing cold email templates for this reason). If a recipient feels as though you have taken the time to research them and craft a compelling proposition, you’re more likely to get a response. As a starting point using custom snippets like {{first_name}} or {{company_name}} can make all the difference.

When it comes to email copy, less is often more. To generate a good reply rate, you should send emails that are relatively short and to the point. Decision-makers rarely have time to read unsolicited emails containing endless paragraphs of information. Every single word is precious real estate on the email and you should consider asking a question about the prospect’s process in the area where you can provide value - rather than asking for a meeting on every email in your sequence. 

How can I improve my cold outreach?

The most common theme across businesses that have the highest ROI from cold email is constant iteration on their campaigns and adoption of the best technology in the market to make sure their approach is unique and sincere. Unfortunately, many people begin using cold email with the incorrect perception that it should be a ‘cheaper’ acquisition channel - However, businesses that understand cold email is a valid acquisition channel due to its consistency and scalability are in a position to adopt the following best practices inside their outreach strategy to see better results:

  • Ensure your cold outreach is being sent through the email client (meaning an actual Gsuite or Microsoft account), not a 3rd party SMTP sender. 
  • Invest in an inbox placement platform to increase the percentage of your email which reaches the primary inbox. (if your emails land in spam / promotion folders there’s no point sending them)
  • Space your email sending across the entire day based on the time-zone of your prospects, with a minimum delay between each email. (from early morning before work starts, all the way through to late evening). 
  • Don’t use email alias accounts (even though they are cheaper - instead, use business Gmail or Microsoft accounts). 
  • Ensure you are spreading your prospecting across enough email accounts, you should look to not send more than 100 emails per day per email account. (we’d advise picking a limiting number like 83, and simply having multiple email accounts to conduct whatever volume you need).
  • Start your email sending through the automation platform with a slow ramp  / steady increase so you’re building the sending volume to your target daily number over 14-30 days. 
  • When you’re creating the email accounts you’ll use for prospecting emails, name them after a real person who works at the business and ideally someone in a senior position. 

Finally, consider cold outreach as a long term acquisition channel that you’ll rely on building properly over multiple years. With this mentality, you won’t be tempted to cut corners or costs in the set-up of your go-to-market process. 

What is email domain reputation?

Email domain reputation is one of the primary factors which influences where inside a contact’s inbox your emails land. Allegrow enables you to track your spam score and any changes to your reputation in real-time. Monitoring your email domain reputation over time will allow you to adapt which data/contact segments you target, the volume of emails you send and the content you use so that every email you send has the maximum possible impact and engagement. 

Consider email domain reputation as being like a credit score that ISPs (inbox providers like Google, Microsoft, Yahoo etc), use to assess where your email should be placed in their user’s inbox. If you have a low score, email providers are more likely to place your email in the spam or unfocused folders that prospects don’t check. Whereas, if you have a high score you’re likely to be placed in the primary inbox so prospects can see and engage with your email. 

Similar to a credit score in real life - if you build great engagement and history your score will increase. By understanding the criteria email providers use to calculate the score you can take steps over time to improve and monitor it - this is what we have dedicated our resources to helping businesses achieve using our technology and network of real business email accounts. 

How to check domain reputation + Flaws in the current methods?

Currently, technology solutions in the market which allow businesses to measure/calculate their domain and sender reputation follow these 3 principles:

1. Emails will be sent from your domain/email account(s) to other external inboxes. 

2. The provider of the monitoring solution has the ability to access and log where inside these inboxes the emails which have been sent landed. (meaning the folders: inbox,  spam, social, updates, promotions, unfocused, junk).

3. The provider of the monitoring solution uses the data on what percentage of the overall sent emails landed in the primary inbox to calculate the sender reputation and report this back.  

Now, it’s important to remember that the purpose of this entire process is to provide you with data that helps you make marketing decisions. Therefore, the quality and accuracy of the data you receive from this process is vital (otherwise you may as well not conduct the test). 

There are a few areas we’ve noticed most tools on the market have clear slip-ups / flaws which make that data from their platforms ineffective in the context of professional marketing, to save you wasted time and resources operating on incorrect data we’ve itemized the main flaws in monitoring and warming which you should look out:

  • The Inboxes used in the network:
    Most platforms use email accounts that are set up or purchased in bulk by the monitoring provider (you may hear these networks being described as ‘private’). The issue with this process is that the email addresses in the network are not unique domains or representative of real business inboxes (ESPs know when an account is fake). Therefore the data you get on inbox placement from networks made from these inboxes is inaccurate and won’t show the variation in sender reputation which marketers rely on to make decisions. To clarify, inside Allegrow our network is crowdsourced and built from unique B2B inboxes (meaning other Allegrow users' real inboxes), therefore, we’re able to provide data that is representative of a real prospecting audience.

  • The sample size and period to calculate the score:
    Many testing platforms will either (a) send a relatively low number of emails, meaning under 100 and run a reputation rate calculation from this data or (b) send a batch of emails to calculate reputation rather than continually sending emails over multiple days/weeks and calculating the average score based on multiple data points. To be completely candid, using a solution that works with these sample sizes or single/one-off batches will be ok to use for free if you’re just getting started running cold emails at a very low volume. However, if you’re a serious professional marketer then these sample sizes will not be statistically relevant compared to the number of emails you send.

  • Separating monitoring from interaction relationships with inbox providers:
    Many warming tools on the market do not separate the domains inside their network which interact with your account, from monitoring domains. This means the email domains that respond to your emails, move them out of spam, mark them as important etc, are also the same domains that calculate your sender reputation over time. Now the clear issue here is due to the fact email domains effectively have a ‘memory’, meaning, if you have a low reputation and send an email to me tomorrow which lands in spam and I proceed to move your email out of spam and/or respond to it, even if you’re reputation rate doesn’t change future emails you send to my inbox are very unlikely to land in spam as my preference to interact with you is remembered by my mailbox provider. Therefore, platforms that use the same mailboxes for both interacting and monitoring will inevitably show reputation data which becomes less accurate (and usually always higher) the longer you use the platform. Allegrow, on the other hand, separates monitoring relationships from interaction relationships using a complex structure - meaning the inboxes which we calculate your score from will not interact with you positively, instead these interactions are conducted from other inboxes in the network.

How can I improve my email reputation?

Assuming you want to send marketing as well as have a high sender reputation, you should strike a balance between volume, personalisation and follow-up in your outbound campaigns. You’ll be able to track how your reputation is changing inside Allegrow. Consider the email limits of your specific provider so you’re coordinating outbound emails being sent across the right number of email accounts.

Implementing an inbox placement solution to increase the positive engagement which ISPs observe on your domain via replies, emails being marked as important, and messages being moved out of spam when they land there, will help to improve your sender reputation over time. Even if you’ve already implemented an inbox placement solution, you’ll want to ensure the platform you connect to (a) has a network made from real business inboxes, not bulk purchased/set-up ones by the provider of the solution (b) uses a multi-day/week large sample size to calculate your score, not a single sending batch and (c) separates relationships between inboxes for monitoring and interactions in its network.
The sentiment prospects have towards your emails will be a primary indicator of your sender reputation. For example, if they want to engage with them and respond to your emails you’re on the right track to consistent primarily inbox placement in the long term. Whereas if prospects you email get annoyed by your emails and choose to actively mark them as spam inside their email client your account is likely to have poor inbox placement and struggle to ramp sending volume without account shutdown.  

Finally, by considering the best practices we’ve outlined across the entire post and implementing an inbox placement solution, with the viewpoint of email outreach being a long term customer acquisition channel you will be able to build a strong sender reputation and success over cold email.

How does an email warm-up tool work?

An email warm-up service is designed to increase your sender reputation and inbox placement over time, so that less of the marketing and sales emails you send land in spam or unfocused folders - meaning your emails are opened, read and engaged with by more prospects. 

The aspects of warming solutions that lead towards this increase in sender reputation can be delivered across multiple features (for example with Allegrow our: content testing, interactions and monitoring help deliver this increase), however, the interactions aspect of solutions that conduct warming are composed of these simulated actions inside your email accounts:

  • Responses to emails that have been automatically sent by you. 
  • Emails that you’ve sent being automatically marked as important inside inboxes from the network. 
  • Inbound emails will be received by your inbox from other accounts in the network. 
  • When your emails land in spam folders inside inboxes from the network, they will be automatically marked as ‘not spam’ a portion of the time. 

The act of these processes being conducted inside the Allegrow network sends signals to ESPs that emails from your domain are trustworthy and important. Therefore, as this process continues over time, being conducted with real inboxes, you can track improvements on your spam score and domains reputation. 

If you’re ready to get started with an inbox placement platform today -  Get started with Allegrow today!