The significance of your email sender reputation and its impact on engagement

email sender reputation

Email marketing plays a vital role for every marketer. In fact, many solely rely on this channel to generate new sales, therefore ROI expectations are always high. Which is why marketers need to be doing everything they can to ensure their messages are even being received by their customers. Most don’t give much thought to the delivery of the email itself – but they absolutely should. In this article, we explore email sender reputation and how IP and domain warming can help you achieve it!

What exactly is an email sending reputation? 

Everyone has a spam/junk email folder, but have you ever wondered why certain emails are automatically sent there or to a dedicated social or promotional folder? 

In fact, not all emails even make their way to your inbox, some get blacklisted completely. So why does this happen? What makes your mailbox take these actions?…….Well, it all comes down to the sender’s reputation.

Marketers send a substantial amount of emails to their customers, yet very few understand the impact that Internet Service Providers (ISPs) have on the successful delivery of their emails. ISPs are highly sensitive and get suspicious very easily. For example, when: 

  • a new IP or domain starts to send obscene volumes of emails
  • an existing IP or domain sends a high volume of messages containing the same content
  • an email hasn’t been sent by an IP or domain for 30 days or more
  • an IP or domain practices poor data hygiene (by continuing to send to non-existent inboxes for example)
  • the IP has been previously blacklisted

Email sender reputation is extremely important in ensuring your messages are reaching your intended audience and thus have the chance to be opened and read. The number of ISPs that reject the message will have an impact on your overall send, as other ISPs who would’ve typically released the email will identify the ISP rejection and could follow suit! 

There are a number of free resources online for you to check how healthy your email sender reputation is, including: Sender Score and Cisco Talos Intelligence. You can also check if you’ve somehow inherited an IP address that was abused in the past through Spamhaus.

How to improve your email sending reputation

It takes time to establish a healthy sending reputation and it’s only achieved by following the best practices (there’s no quick win here), which is why we always recommend IP and domain warming to our clients. Essentially, IP and domain warming is an opportunity to develop your identity and gain trust from the ISPs. Let’s break this down further.

Domain warming

Often overlooked, but equally important as IP warming is the reputation of your domain. For example, Customology’s domain is, so if one day we decided to start using instead, we’d have to rebuild the high sender reputation we had already achieved. Some brands chop and change their domain names when sending out comms to their customers, when they would see much higher engagement by remaining consistent. If they insist on making a domain change, it should be subtle such as, i.e. a common ancestral change rather than a whole new domain. 

It’s best to plan ahead when choosing a domain name – picking one that makes sense, aligns with your brand and content and has longevity. If you have an already established sending domain, you’ll be in an even stronger position. 

IP warming

If a device is able to communicate via the internet, it will have an Internet Protocol address, more commonly known as an IP address. A dedicated IP is an IP address specific to an individual user. A shared IP address is used by multiple users, meaning each of these users can impact sender reputation. 

The IP warming process involves sending small volumes of emails from a new/inactive IP address, gradually increasing the volume of sends across a period of time (days, weeks etc.). The warm-up schedule is different for every user and depends on how many emails you intend to send. If you send out a high volume of emails (i.e. 500,000+ a week), then we recommend you use a dedicated IP address to do so.

Martech platforms, such as Vector enable you to automatically limit or cap the number of emails you send each day/week, taking away the manual process of continuously logging in to schedule your sends. 

We recommend that when you begin sending customer communications from a new IP address, you send your first batch of emails to your most engaged customers, as they’re more likely to open the email which will give your sender reputation a positive start, meaning the ISPs are more likely to trust you when you’re trying to reach less engaged customers. 

It’s important that you have visible metrics for engagement and good ‘hygiene’ on your ongoing sends too. Metrics such as delivery, open, click and click-to-open rates will give you feedback on each of your sends and pruning disengaged recipients from future email sends is important for a healthy sending reputation. You can try to reach these customers via another comms channel.

It’s worth mentioning that if you do stray too far with reasonable sending and end up getting marked as spam by an ISP (greylisting or blacklisted) then there’s no clear industry standard about how long you have to wait to try again on that IP and sending domain. ISP’s do have a finite memory however, so you can try again but it would be best to start the entire warmup process again costing you time and money.

Maintaining a strong email sender reputation

Once you’ve undertaken both domain and IP warming, the hard work doesn’t stop there. You’re constantly being monitored by the ISPs, so it’s important you do everything in your power to maintain your strong reputation, including:

  • maintaining good data hygiene – i.e. remove email addresses that hard bounce, list-unsubscribe or invoke a spam complaint
  • honouring email opt outs
  • having good email acquisition from the start (i.e. a two verification process, as this proves if you send an email, they have the ability to receive it from the get go).

ISPs respond well to engaged mailboxes. We often reference that “no one size fits all”, especially when it comes to marketing communications. Therefore, if you have a sophisticated comms strategy, segmenting and targeting your customers effectively, then your customers are more likely to engage with the message – ultimately ensuring an even stronger sender reputation.

Achieving cut through in today’s busy marketplace is proving more challenging by the day. Brands need to ensure that any obstacles preventing them getting their message in front of their intended audience are removed. IP and domain warming greatly improves your email sender reputation, which in itself brings a number of benefits. It’s an imperative in today’s digital world!Keen to learn more about email sender reputations and how to improve yours? We’d love to help, contact one of our Customologists today on 1300 264 549 or

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