Best Practices for Email Deliverability

Follow the below best practices to achieve and maintain good email deliverability.

Optimal Set up:

  • Make sure you are compliant and your email setup is correct.
  • Ensure audience collection points are clean.
    • Use double opt-in, if possible.
    • If not, use a single opt-in with captch at the signup point to avoid bot signups.
    • Do not send marketing/promotions to users if they have not explicitly signed up.
  • Ensure email send frequency is proportional to end user’s engagement levels.
    • Send less frequently to less engaged users.
    • Consider retargeting campaigns for unengaged users.
    • Use Frequency capping to limit the emails sent per user per day/week.
      • Sending too frequently results in user fatigue which increases spam complaints and unsubscribed.
  • Set correct expectations and be open and clear.
    • Set correct expectations while collecting users and stick to those.
    • Subject lines and pre-header text must never mislead the users about the content of the email.

Steady Sending patterns

  • Maintain steady sending patterns to ensure IP and domain remain warmed up.
    • Send at least 1 campaign a week to active users.
    • Send at least 1 campaign every 2-3 weeks to the ramped-up volume / all opted-in users [barring the suppressed inactive users].
  • Make sure you are warmed up to send the intended volume.
  • Use the correct RPM to throttle the emails.
    • If you send too fast without ramping up, it will result in delivery issues.
    • Refer to RPM recommendations.
  • Do not suddenly increase volume.
    • Peak season campaigns tend to include less active/inactive users.
      • Prepare for peak season mailings at least 6 weeks in advance.
    • Important announcements can be sudden.
      • Make sure these are text-only and throttled/split over the day/s well.
  • Ramp-up instead of resuming after inactivity.
    • IPs and domains get cold when inactive.
      • Start slowly by sending to highly engaged users.
      • Slowly expand to other users with lower email engagement.
    • Do not send higher volumes at once.
    • Send to email openers only, with higher throttling (low RPM).

Dynamic Strategy

  • Maintain a 70:30 ratio for Active v/s Inactive Users.
    • The major portion of the target criteria should be active users.
    • This helps keep the overall negative engagement low.
  • Send event-based personalized campaigns like event-triggered and flow campaigns.
    • Use cases for e-commerce brands can be found here.
  • Make sure content is relevant to the users.
    • Sending irrelevant content makes people lose interest in the sender.
  • If engagement levels drop, reduce send frequency and send targeted content.
    • Survey to find reasons for disinterest.
  • Suppress inactive users if there has been no engagement in 6+ months (or less/more depending on the industry.)
    • ISPs like Comcast, Yahoo, and so on, disable unused mailboxes.
    • If mailbox providers themselves have policies to suspend users, it’s imperative that the sender also have strategies to suppress them.

Monitor and Revise

  • In case of issues:
    • Deferrals i.e. rate limited by ISP.
      • Use lower RPM
      • Look into sending patterns.
      • Pause for a day, let the IPs rest, and raise a ticket with postmaster support.
    • High user-reported spam complaints/unsubscribes:
      • Reduce sending frequency
      • Check whether the content is relevant to each segment.
    • Low opens/clicks
      • Send only to email openers
      • Review the target audience
      • Review FC settings
      • Ensure content v/s segment relevancy.
      • Pause and monitor.
  • In case of domain reputation issues, check here.


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