March 27, 2018

11 Best Practices to Improve Email Deliverability

Reading time about 17 min

There’s nothing more frustrating than spending time creating an email marketing campaign, only to have 50% of your contacts fail to receive it because you ended up in their spam folder. That’s why following email deliverability best practices is so important.

If your emails are failing to be successfully delivered to your contacts’ inboxes, you should be focusing on ways to improve your email deliverability. But, even if you don’t have problems getting to the inbox, it’s still important to avoid making any mistakes that could damage your deliverability down the line.

Although the end goal and concept of deliverability is simple, there are several factors on which it depends, including:

  • Sender reputation – How have your previous emails performed and has your domain or IP behaved dubiously in the past?
  • Email content – Does your email campaign look like spam?
  • Technical aspects – Are your emails properly signed with the right domain and IP? Has the content been altered in any way?

If you’re still a little unsure of how this all adds up or what you can do to improve deliverability, don’t worry.

We put together a list of 11 effective deliverability best practices for you to follow so you don’t have to worry about getting stuck in spam anymore!

Basic Email Deliverability Best Practices

We’ll start off with the more basic best practices that you can do to improve email deliverability and be a better email marketer.

These best practices apply to senders of any volume, and they don’t require any technical knowledge or skills.

1. Clean out old and unengaged contacts

Periodically cleaning your email contact list is one of the most important things you can do as an email marketer.

While keeping old or unengaged contacts may seem like a good idea (or at least a good self-esteem booster), it can hurt your email engagement rates and your overall deliverability.

In particular, there are two types of email addresses that can cause you problems:

  • Non-existent email addresses
  • Unengaged or inactive email addresses

It’s a good idea to delete both of these groups of contacts from your database if you want to maintain good deliverability and avoid being penalized by email providers like Yahoo and Gmail.

Remove non-existent email addresses

Within the category of non-existent email addresses, there are two types:

  • Email addresses that were incorrectly entered by the subscriber
  • Old email addresses that are no longer being used

For the first type, you can prevent misspelled addresses from entering your contact database in the first place by implementing a double opt-in process for signups. We can’t recommend doing this enough, especially in light of the GDPR and the increased need for positive consent.

For old emails that are no longer being used, Sendinblue actually does most of the work automatically.

When an email address produces a hard bounce, they are automatically blacklisted in our system. That means they won’t be able to receive any more emails from your account. This usually occurs when a user stops using an email address and deletes it.

You can see all of your hard bounces by filtering them in the contacts page in your account.

hard bounces damage email deliverability

While this might seem like enough to combat non-existent email addresses, there is still one big piece that’s missing. Sometimes, email providers will turn an abandoned or deleted email account into a “spam trap.”

Failing to blacklist spam trap emails can take a massive toll on your deliverability. So be sure to not only remove hard bounces but also check back in with any contacts who were added more than a year or two ago. That leads us to the second category of contacts to clean out:

Remove unengaged email addresses

Inactive or unengaged contacts also hurt your deliverability. The reason is that they lower your engagement rates for your campaigns, which ties back to your sender reputation with email providers.

There are a number of reasons why a contact might become inactive:

  • Your emails aren’t reaching their inbox because you’re being filtered into spam
  • The contact is no longer interested in your business
  • The contact receives too many emails and yours are being lost in the mix

Whatever the reason though, you should re-engage with these contacts and ask them if they still want to receive your emails. If they’re no longer interested or don’t respond, remove them.

To do this, you can sort your contacts in Sendinblue based on whether or not they have opened an email in the past 6-12 months.

Create a filter using “Between” and set it for between 365 (or however many days you want to check) and 0 days before today. You can then save this filter for future use by clicking the “Save” button. After saving it, you can access it by clicking on “My Filters.”

clean out inactive contacts for better deliverability

Once you have these contacts, add them to a list of “inactive contacts.” From there you can re-engage them using a more targeted approach.

One tactic could be to send them an email that asks if they would like to continue receiving emails from you with a “Yes” and “No” button. If they click “No” or don’t respond within a week or two, remove them from your list.

You can also do this with automation.

Create an automation workflow that checks whether a contact has engaged with your previous 10 email campaigns (you can choose a different number that makes the most sense for you), and adds them to a list of “inactive contacts” if they failed to do so.

Once they are added to this list, automatically send them a message asking if they are still interested in receiving your emails. Have the workflow wait a week or two, then remove any contacts that didn’t re-opt-in.

re-opt-in email list cleaning

2. Send only to contacts who have opted into receiving your emails

As we mentioned earlier, engagement rates play a big part in determining your sender reputation, and ultimately your deliverability.

Sending emails to contacts who have not opted into your list (by means of a purchased or scraped list) will result in much lower engagement since these recipients haven’t shown any interest in your product.

This will undoubtedly hurt your deliverability and is the reason why we always advise against purchasing lists.

But, simply not purchasing contacts isn’t enough these days. With more savvy users and new laws like the GDPR going into effect, you have to be very clear about what subscribers are opting in to receive.

Use clear language on your opt-in forms so you don’t upset your contacts with unwanted emails. This ensures your contacts actually want to read your emails, resulting in better overall engagement and better deliverability.

Also, don’t forget to use a double opt-in process! 🙂

3. Avoid spam filters

Whenever an email is received by an email provider, the content is scanned to check for spam content.

This filter is looking for specific types of content that typically indicate spam, such as:

  • Writing in all caps
  • Using too much punctuation (don’t write 10 exclamation points in a row!!!!!!)
  • Using red font
  • Overuse of spam words (free, cheap, pre-approved, $$$, 100% free, urgent, don’t wait!, etc.)
  • HTML errors

If you avoid making the mistakes above, you should be able to pass through this step pretty easily.

4. Pay special attention to your subject lines

Subject lines are the literal front lines on the battlefield that is email marketing. The content you include has a substantial impact on the performance of your emails, which also affects deliverability.

When creating your subject line, you really have to keep in mind two things:

  • Don’t make false promises – Clickbaity subject lines that oversell the content in your email may seem like a good idea (it gets them to open, right?), but it will hurt you down the road. If your users feel like the value of your email content isn’t what you promise, they’ll get frustrated and unsubscribe — or worse, report you as spam. That will kill your sender reputation.
  • Make the subject line interesting and relevant – As we mentioned in the point above, you shouldn’t oversell your content. But, you should still make your subject line enticing and relevant. This will attract more openers and boost your sender reputation.

For tips on how to optimize your subject line, check out our help article on the topic.

5. Make sure the sender is easily recognized as you

When your email shows up in your customer’s inbox, you want to make sure they know it’s from you. You wouldn’t ring someone’s doorbell with a mask on, right? (unless it’s Halloween of course 😉 )

In all seriousness though, you want your marketing emails to look professional.

One thing you can do to help is make sure you’re using your business website domain in the sender email address. This helps you avoid giving off a sketchy vibe and lets your contacts take you more seriously.

When setting the sender name (the name that appears as the sender in the inbox), choose a name that includes your business name in it as well.

For example, I send our newsletter as “Jeff @ Sendinblue.” That way, recipients know that it’s coming from Sendinblue, but with the personal touch that comes with adding my name. You can also go with the classic “[Company] Team,” though this isn’t as personable.

Setting sender name and address

If you use your normal first and last name, recipients won’t know it’s from you and they might just delete it straight away.

6. Send consistently

Consistency is another important factor for improving reader engagement with your email campaigns. Find the right timing and frequency helps by:

  • Placing your email in readers’ inboxes at the time when they’re most active
  • Creating expectations for your readers so they know when to look out for your new campaigns

Finding the right time of day or day of the week to send emails may take some testing — every audience is different. But it will pay off in the end.

Both of those increase the likelihood that contacts will open and click on your emails. And remember, anything that improves engagement, improves deliverability as well.

7. Follow email marketing best practices

As we mentioned a few times already, a big part of improving deliverability is getting more contacts to open and click on content in your emails. The best way to achieve that is by following basic email marketing best practices:

  • Send content that your users actually want to read – Readers give you their contact information so they can get something of value from you. Whether it’s discounts, exclusive tips, witty content, or something else, there has to be something in it for them or they won’t engage. Make sure to always ask yourself if your content will provide that value before hitting send.
  • Make it easy to unsubscribe – I’ve said it before, and I’ll say it again: you do NOT want to keep contacts in your list if they aren’t interested in your content. This will only hurt your engagement. Make it easy for them to unsubscribe if they’ve lost interest — otherwise, they might get frustrated and just send you to spam. That is far worse than losing a subscriber.

Advanced Email Deliverability Best Practices

Now that we’ve got the basics out of the way, it’s time to get a bit more technical.

Here are a few advanced steps you can take to improve your email deliverability even more.

8. Avoid using free email provider domains

When setting up senders in your email marketing account, you should avoid using free email provider domains like Gmail (others include AOL, Yahoo, etc.).

Many of these providers have adopted a DMARC policy (more on this soon) that tells email inbox providers to reject any emails that don’t have the proper technical signatures.

For example, if you’re sending an email with a Gmail address through a third-party software like Sendinblue, and outside of the Gmail framework, your message will be rejected. This is done to prevent phishing scams and other types of attacks using the Gmail domain.

Important Note: If your Sendinblue plan sends email from our shared IP addresses and you continue using a Gmail sender address, we will modify your sender so that your messages are deliverable. Your sender email address will be changed as follows: will become If your Sendinblue account sends via a dedicated IP address, we will not alter your sender address. Your emails will continue sending from your Gmail sender, and these messages will be rejected / not delivered by many ISPs and inbox providers.

So, instead of using a free email address for your sending — set up a sender that uses your own domain. This looks more professional anyways. 🙂

9. Consider using a dedicated IP

Most email marketing services have a range of IP addresses that are used for sending emails.

These IP addresses are often shared by multiple customers. This means one customer’s sending behavior can affect the reputation of other senders on the same IP address.

Luckily, Sendinblue and most other email marketing providers perform checks on new users to make sure they aren’t going to abuse the platform and hurt the deliverability of other users.

If you still have concerns, there is another option. Sendinblue offers dedicated IP addresses, which allow you to take full control of your sender reputation.

This is usually only a good idea if you send a high volume of emails though, as dedicated IPs require consistent activity to maintain a good reputation with email providers. At Sendinblue, we automatically include a dedicated IP address for all of our Premium Gold accounts (350,000 emails/month).

Do some research to decide if you should use a shared IP or dedicated IP while using a lower volume plan. If you have questions, our customer care team is here to help! Email them at

10. Set up a dedicated subdomain for your email marketing

As we mentioned earlier, it’s a good idea to use an email from your own domain as the sender of your campaigns to avoid any problems with email providers.

But, it might also be a good idea to take this a step further and set up a dedicated subdomain that is just for sending your marketing emails (e.g. set up the subdomain That way you can separate the reputation from your website domain and your email campaign sending.

Learn more about delegating your subdomain as the sender in Sendinblue in this article.

11. Configure your DNS records with the proper SPF, DKIM, and DMARC signatures

We talked previously about the DMARC policies of email providers like Gmail and Yahoo that instruct email inbox providers to filter out your messages if you’re using their domain to send mass emails outside of their system. But, it’s also possible to set up a DMARC policy and the underlying security frameworks to improve email deliverability on your domain as well.

DMARC is built on top of two protocols used for email authentication:

1. DomainKeys Identified Mail

DomainKeys Identified Mail (DKIM) is an authentication mechanism that enables the email recipient to check the digital signature of a message and verify that it was authorized by the sending domain using the public key in that domain’s DNS records.

Think of DKIM like a unique seal on an unopened package that you can use to know if it actually came from the right person.

This prevents someone from sending emails with your domain posing as you (a.k.a. email spoofing). It also provides some assurance that the content of the email has not been modified since the signature was attached.

2. Sender Policy Framework

Sender Policy Framework (SPF) is another framework that helps the receiving inboxes determine the legitimacy of the sender and prevent email spoofing. SPF works by having the sender establish authorized sending hosts (IP address of the machine sending a certain message) in their DNS records, making it easy to identify spammers using forged email addresses under your name.

You can kind of consider it like a VIP guest list. Even if you say you’re VIP, you’re not getting in if your name’s not on the list. The same goes for SPF: if the sending IP for a message being sent by “” is not in the SPF records for, that machine (IP address) is not authorized to send messages using that domain.

Set up DKIM and SPF with Sendinblue

If you’re using Sendinblue, you can easily get the correct SPF and DKIM records to set up your own DMARC policy with your business domain’s DNS records.

This is possible for users of both our shared IPs and dedicated IPs, and it’s always a good idea if you want to make sure that no bad actors are using your domain for spamming or phishing scams.

Wrapping up

Hopefully, you have a better understanding of how your various factors affect your ability to reach your contacts’ inboxes and what you can do to maintain good email deliverability.

Remember the key takeaways:

  • Maximize meaningful engagement with your emails
  • Only send messages to contacts who want to receive them
  • Make sure your technical specifications are set up properly with your DNS provider

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