How to find your email in Gmail with tabs & category labels
Gmail will sometimes put your incoming email into different tabs, which can make it difficult to find.
Note the different tabs - Primary, Social and Promotions
Gmail categorized email messages automatically based on their preference and your past actions.
For further description about Gmail tabs check on this link https://support.google.com/mail/answer/3055016?hl=en
Click on the different tabs to see the different emails in each category
Mailing list messages will frequently go to Promotions tab as noted above.