Email deliverability checklist – how you can avoid the spam folder

By Seema Patel on 15 Nov, 2022

Email remains one of the core channels of communication. With so many organisations competing for engagement, ensuring your emails avoid the spam folder and reach your audience’s inbox is a vital part of your email marketing strategy and overall marketing efforts.

Here’s our top tips on setting yourself up for email deliverability success and how to protect your domain reputation.

Ensuring email deliverability success

1. Have a clear IP warm-up plan

To allow a recipient to consider you a safe sender, you need to have an Internet Provider (IP) warm-up plan in place.

The idea is to warm up your dedicated IP address and sender domain in order to improve the deliverability of deliverability of your email campaigns.

A well-designed IP warm-up plan will help you overcome those initial hurdles when you start sending to Internet Service Providers (ISPs) or if you are returning to large-volume sends after going cold for a prolonged period.

2. Establish domain authentications

Before a new email campaign is deployed from any sending domain, basic mandatory domain authentications need to be in place to ensure ISPs recognise you as a bulk sender.

This is required along with the basic Domain Name Server (DNS) configuration that your Email Service Provider (ESP) will ask you to implement.

If any of the below is not in place, you’re likely to have a high rejection rate against most of the ISP domain family.

DKIM (DomainKeys Identified Mail)

SPF (Sender Policy Framework)

DMARC (Domain-based Message Authentication, Reporting and Conformance) to assist with deliverability of your campaigns is also recommended but not essential.

3. Determine who you are communicating with

Decide who you are sending to within your email deliverability testing programme.

The IP warm-up plan needs to be designed around the data you have available. An IP warm-up email should ideally be sent to the entire ‘active customer’ database. ‘Active’ is defined as customers who have opened and clicked an email within the last 12 months and avoid sending to contacts with invalid email addresses.

If you don’t, you risk a negative impact on your IP and your sender score rates will drop, which could result in your delivery volumes dropping. A ramp-up plan sets the scene for future sends. It’s imperative that you build a strong IP reputation from initial execution of your plan.

4. Focus on content

Depending on your circumstance, your first campaign could be a generic email to keep recipients informed and prompt them to interact positively with the email. An example of this could be – “We have now changed email service providers. Please save this domain to your favourites”.

It’s important to have an engaging subject line that will encourage opens. Avoid using spam words such as those that make exaggerated promises as this can impact your email deliverability too.

Ideally, your first campaign should not contain time-sensitive content. The email message will be sent over a pre-determined duration of time, so removing time-sensitive copy reduces the risk of sending an untimely email.

It’s advisable to send your campaigns as Multipart MIME (HTML and TEXT together), as this will help increase your email deliverability rate. Any customers unable to view the HTML can view the text version. Firewalls, whitelisting domains, Ips, and SSLs, can affect viewing and delivery of emails to corporate email addresses and mobile devices.

5. Create a plan

Take the time to plan your ramp-up. Consider what message you want to communicate to your recipients. Some top tips and considerations when organising your plan are:

Split data - according to the major ISP domain families i.e., Microsoft (Hotmail, MSN, Outlook), Yahoo (Yahoo, Rocketmail, Yahoomail), Gmail, (Googlemail, Gmail), AOL and other.
Send throttling - start with small volumes per ISP domain family and increase daily so you are sending 24 hours a day, 7 days a week.
Duration - typically, an IP warning plan would last up to 30 days or potentially longer.
Review your results – take time to review them daily.
Expect to make change based on results – decrease or increase the sending throttling volume, or stop the ISP domain family send and wait for a resolution or guidance from the ISP.
Be prepared for delays if an ISP rejects your attempts to warm up the IP reputation.

6. Consider consistency

Having a plan for post-IP warm-up is just as important as the initial plan itself. Sending frequently is key:

Keep sending email campaigns at, ideally, the same volume rate as the previous campaign(s). ISPs have recognised you and will allow your emails to arrive in a customer’s inbox, as opposed to being blocked or going into the junk folder.
In some instances, you can pre-warn ISPs, such as Microsoft, that you will be sending to their domain family. You can do this in collaboration with your chosen ESP, who will have an established process and relevant contacts for such a conversation.

Use your most active data. This way, you are sending to customers who have verified email addresses and who are genuinely engaged and will be less likely to bounce. These customers should recognise that they have signed up to your mailing lists.

Immediately pause your sends if you see a block or high soft bounces and contact the relevant ISP to remove the block. If you have regular deliverability issues due to infrequent sending, you can use Return Path inbox monitoring and/or tools provided by the ISP, or your ESP may help monitor the situation.

7. What to do if you experience high bounces, abuse, and unsubscribes from major ISPs

Once the campaigns have started deploying, regularly monitor the reporting of each mailing to see how successful your email campaign is by domain.

If you see any anomalies like a high bounce rate, abuses, unsubscribes, opens, and clicks, reach out to your ESP provider who can investigate and let you know the possible cause and resolution of the issues.

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