If you are getting no mail, or getting not enough mail, first consider the possibility that nobody sent you mail recently. Wait a few hours, or even a day or two, before concluding that something must be wrong.
Check our official announcements (see Where to Find Announcements and Discussions) for the last few weeks, to make sure that no major system change has occurred that might be associated with the problem.
If you are sure that there really is a problem, please begin by making sure your custom domain, if any, is functioning normally. To do this, please see Diagnosing Domain Problems.
Once you have verified that your custom domain, if any, is functioning normally, you may proceed to the next step below.
Find at least one person, and preferably two or three people, who actually sent you mail that did not reach you. Ask each of these people to tell you what happens when they send you mail. Does the mail silently disappear? Or does it bounce back? If it bounces back, what does the error message look like?
If you can find only one person who cannot send you mail, or if you can find multiple people at the same service provider who cannot send you mail, then consider the possibility that the problem might be at the sending end. Ask the senders to report the problem to their service provider.
Also check your own spam filtering settings and make sure they are not coming in the way. You can temporarily switch off all spam filtering and see if the senders can then send you mail. For instructions, please see Adjusting Spam Filters.
Once you have done all of the above, please provide the following diagnostic information to us.
MENTION that you did not find a solution in any RECENT OFFICIAL ANOUNCEMENT.
MENTION that you tried disabling all spam filtering on your account and that it did not solve the problem.
If you are using a custom domain, MENTiON THAT YOU HAVE CHECKED YOUR DOMAIN and the domain is functioning normally so far as you can tell.
Mention that you have TESTED WITH SPAM FILTERING DISABLED, so you are sure that the loss of mail was not caused by spam filtering.
Tell us the EMAIL ADDRESS OF at least ONE SENDER who could not send you email, the DESTINATION EMAIL ADDRESS to which each such sender was trying to send mail, and what happened. If the message was silently lost, please say so. If it bounced back with an error message, please MENTION THE ERROR MESSAGE.