ISP Best Practices for Deliverability

    Microsoft Outlook

    When it comes to email deliverability to Microsoft they do things a bit differently than some of the other large email providers.  They are primarily focused on the sender reputation that is created by Microsoft.  Here are some of the more important factors when emailing to Microsoft.

    • SPF and DKIM authentication
    • Clean Content
    • Outlook Reputation

    Microsoft will use their Smart Network Data Services to keep track of the data coming from individual senders.  The SNDS can be viewed for sending information and to help senders improve their sending reputations with Microsoft.


    Gmail puts a lot of weight into customer interaction with emails.  The more interactions a sender has from its users the more likely their emails will continue to send. Here are some of the most important things to note when sending to Gmail.

    • Have Double Opt In or Confirmed Opt In
    • Send content that the recipient is most likely to open and interact with
    • Send to clean and known lists only
    • Set the unsubscribe as the header of the email instead of the bottom
    • Authentication with SPF and DKIM
    • Use sub domains to send to specific groups of customers for different interests

    If Gmail believes that the emails are not getting any interaction then it will start to mark the sender as a less reputable sender, making it harder to get emails to Gmail for future sends.


    AOL measures sending reputation in its own unique way.  Here are the factors that are most important when sending emails to AOL.

    • DKIM Authorization
    • IP Based Whitelisting / AOL Reputation History
    • Email with Clean Content
    • Spam Traps
    • Registered Complaints

    If the AOL spam filters determine that these items are not looking to their standard then they can either flag an email as spam or block it from entering entirely.

    in Deliverability

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