ISP Best Practices for Deliverability

Overview

Each Internet Service Provider (ISP) has different measures of sender reputation. Use the following guidelines to increase your deliverability across all providers.

Microsoft Outlook

Microsoft's metrics are different 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 uses 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

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 determines 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

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 allowlisting / 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.