Although there are many articles online about how to prepare a mailing so it doesn't end up in spam, many businesses still fall into the same traps time and again. From our experience as an email marketing service provider, many deliverability problems with mailing campaigns start at the level of constructing the email itself. Check whether you're making these mistakes and that's why your mailing isn't reaching recipients.

Technical requirements

Domain authentication

From February 2024 Google and Yahoo have introduced new requirements for email senders. For mass mailings (over 5,000 emails/day), you must configure SPF, DKIM, and DMARC records. But even for smaller sends, proper domain configuration significantly improves deliverability.

In Sugester, go to Settings → Email → Domain Authentication to check the status of your domain's configuration.

Sender reputation

Email service providers evaluate whether messages from your domain are welcome. If too many recipients mark your emails as spam, your sender reputation drops – which means future mailings will increasingly be filtered out. Monitor your campaigns' spam complaint statistics regularly.

Content of the email

1. Text-to-image ratio

Spam filters analyse the text-to-image ratio. Emails that consist mainly of images with little text are more likely to be flagged as spam. Aim for roughly 60% text and 40% images. Every image should have ALT text, and the message should be readable even without images enabled.

2. Avoid spam trigger words

Certain words and phrases significantly increase the risk of an email ending up in spam. Avoid: "FREE!", "CLICK HERE", "100% guaranteed", "earn money", "special offer" and similar. Also stay away from excessive capitalisation and multiple exclamation marks.

3. HTML code quality

Poor HTML code – too complex, with many nested tables, inline styles everywhere, or code copied directly from Word – triggers spam filters. Use clean, semantic HTML. Test the email in various email clients before sending.

Recipient list

4. Only send to people who have consented

This is the basis of deliverability and compliance with GDPR. Don't buy email lists or send to people who haven't explicitly consented to receive your mailings. A small, well-engaged list is worth far more than a large list of disinterested recipients.

5. Regularly clean your list

Remove inactive recipients – those who haven't opened your emails in 6–12 months. Also remove hard bounce addresses (invalid addresses) immediately. Sending to a "dirty" list lowers your reputation and hurts deliverability.

6. Easy unsubscription

From February 2024 this is also a requirement from Google and Yahoo: a one-click unsubscribe option is mandatory. In Sugester this is automatically included in every mass mailing campaign. Don't make it difficult for people to opt out – it's better that someone unsubscribes than marks your email as spam.

Good sending practices

7. Gradual sending

If you're just starting to send mailings from a new domain or IP, start with small batches and gradually increase volume. A sudden spike in sending volume from a new sender is a red flag for spam filters.

8. Sending time

Test different sending times to find when your recipients are most likely to open emails. For B2B, Tuesday to Thursday between 9 am and 11 am usually work best. For B2C it depends more on the specific audience. In Sugester you can schedule mailing delivery at a specific time.

9. Personalise emails

Personalised emails achieve better open rates and fewer spam complaints. Use the recipient's name in the subject line or in the email body. In Sugester you can use variables like {name} in email templates to automatically insert each recipient's data.

How to check if your email lands in spam?

Before sending a mass campaign, test it:

• Send a test message to your own addresses in different email clients (Gmail, Outlook, Yahoo)
• Use tools like Mail Tester (mail-tester.com) to check the spam score
• Check your domain's SPF, DKIM, and DMARC configuration

In Sugester, after sending a campaign you can track its results in the mailing report: open rate, click rate, bounce rate, and spam complaints. Regularly analysing these metrics will help you continuously improve your campaigns' deliverability.