Here’s some best practice for sending bulk emails to avoid mail servers blacklisting them or moving your emails to junk inboxes. The practices are split into technical and behavioural categories:
Authenticate Your Domain
Use SPF, DKIM, and DMARC to authenticate your emails and establish trust with mail servers.
Maintain a Clean Email List
Regularly clean your email list by removing invalid addresses, duplicates, and unengaged users. If you have a high number of users with invalid emails then this can severely affect how mail servers deliver your emails.
Use a Verified Sending Domain
Send emails from a verified linked Web domains instead of generic domains like @gmail.com or @yahoo.com.
Test Your Emails Before Sending
Test your email using the system functionality before sending out to your mailing list to help spot any potential issues.
Avoid Overusing Images and Attachments
Keep a balance of text-to-image ratio, and host large files on external platforms instead of attaching them.
Craft a Clear and Relevant Subject Line
Avoid spammy words like "Free," "Urgent," or excessive use of capitalisation and punctuation.
Engage Inactive Users Strategically
Use re-engagement campaigns to win back inactive users, but remove them if they remain unresponsive.
Send Emails at Optimal Times
Experiment with different times and days to identify when your audience is most likely to engage. For example most users will read emails during a a bus/train commute, lunch break or evenings.
Keep Content Relevant and Concise
Avoid overly promotional language that may trigger spam filters and keep content relevant to the Subject Line.
Encourage Whitelisting
Ask recipients to add your email address to their contacts or safe sender list.
Follow-Up Responsibly
Avoid over-emailing recipients to prevent complaints and unsubscribes. 1-3 emails per week per recipient is a good benchmark. Sending more than this may result in fatigue or unsubscribes unless the content is highly relevant.