Why is Gmail not seeing emails?

Question

gmail

I set up the function in Gmail "Check mail from other accounts (using POP3)", I do a mail check, it shows that one letter has been received, but this letter is nowhere to be found! what could be the problem?

Answer 1

01. Are all types of incoming messages and spam checked (it's trite, but he "missed" the first 2 letters in the new interface, though it's not new anymore)?
02. If there is a suspicion of a virus - Gmail will not let it through: for example, if the attachment is suspicious.
03. If the list is continuous, you need to see by date: the letter can be. received earlier and fixed on page 2 or later.

Answer 2

It is also possible that the new letter did not get into the Inbox folder, then it can be found in the "All Mail" folder.
Are you sure you don't have any filters configured that can do something with this email?