Gmail and Microsoft deliverability tips

Each email receiver/spam filter has its own set of algorithms for receiving email, so it can be a tricky to pinpoint why a message was not received in the inbox (or other emailing classification folders). Gmail and Outlook/Office 365 tend to look at user-specific preferences when filtering email; they look to see if the user typically opens the mail, moves it to a folder, flags as spam, and replies to the sender. While completing sender authentication and maintaining a good sender reputation provide a good foundation for getting email delivered to the inbox, some email filters go beyond those mechanisms and include user engagement.

Some examples of well-known inbox categories are the Promotions tab in Gmail and the Clutter folder in Outlook. Remember, these are not junk folders, but rather special inbox classification folders.

Unfortunately, there is very little a sender can do to guarantee delivery to the inbox or "primary" folder, but below are some resources that can help you define how these user-defined preferences work.

Filters

Most filters look at several things.

• The sender ("from" address/IP address - good or bad reputation)
• Whether sender authentication (Sender Policy Framework [SPF], DomainKeys Identified Mail [DKIM], Domain-based Message Authentication, Reporting, and Conformance [DMARC]) is in place
• Whether you're a bulk sender
• Whether the user has engaged in a two-way conversation
• The user's open rate
• Whether the user moves the message to the filtered folder or inbox
• Whether the user classifies the message as being from a safe sender

Gmail

There are two key things a sender can do to encourage users to route mail to the Primary tab:

• Separate different types of content with a unique "from" address, domain, and/or IP (Internet Protocol) address. This gives users more options when classifying different types of mail. This could mean the difference between all versus some of your mailings going to the Promotions tab.
• Encourage users to classify your mail as Not Spam, "star" them, or move them to a folder. The mailings are more likely to end up in their inbox or Primary tab.

Learn more about Gmail bulk sender best practices.

Outlook/Office 365

For Outlook and Office 365, Clutter and Junk mail are filtered prior to reaching the inbox. When receiving a message that meets the criteria for junk, Outlook/Office 365 places the mailing in the Junk folder. If not, it passes through any custom rules in place so that it can be classified in the corresponding folder. Next, Clutter analyzes the message based on the user's interaction history. Users can turn off clutter and adjust its settings to prevent messages to be classified as such.

Learn more about how Clutter classifies mailings.

Sender tips

Below are a few things that senders can do to help with inbox delivery.

• Complete sender authentication (SPF and DKIM).
• Keep your messages consistent with your "from" address.
• Send to opted-in and engaged subscribers only.
• Encourage subscribers to interact with your messages.
• Ask subscribers to add your email address to their safe senders list to ensure delivery.