See also the FAQ in the Help Center.

Failing to Receive [Some] Group Messages

It sometimes happens that you fail to receive some or all group messages (i.e., via email). Here are some things to check:

• Are the missing posts listed in your account's Recent Bounces page?
• Are they listed in the Email Delivery History tab of your Subscription in that group?
• Were they posted to a Topic that you have muted?
• Is your account in Bouncing or Bounced status?
• Is your Email Delivery set to Individual Messages?
• Is your Message Selection (under Advanced Preferences) set to All Messages?
• Do the missing posts contain a hashtag that has the No Email property?
• Do the missing posts contain a hashtag that you have muted?

• Have you set a filter that blocks or redirects some (or all) group messages?
• Are the group messages landing in your Spam (or Trash or other junk) folder?
• If you're using an email client on a PC or mobile device, have you checked the spam folder of your service's Webmail interface?