Why are Gmail addresses not receiving mailings?

Environment:

Outreach, Mailings

Issue:

Mailings appear to not be sending to contacts having Gmail addresses. The mailing is not showing up in their Gmail Inbox. 

Resolution:

The mailing should be found under the All Mail section of Gmail. By default, under Gmail settings, there are categories selected. These can be viewed by going to the settings button > See all settings > Inbox. The categories are listed in the second section. By default Primary, Social, and Promotions are selected. To allow mailings to be directed to the Inbox, the recipient would need to uncheck Promotions. If mailings are still going into the All Mail section, it may be that they are being categorized by Social rather than Promotion, in which case, that category should be unchecked. The mailings should then show up in the Inbox.