Louis says he's having trouble getting his Gmail lately. Leo says this has been the third caller with this problem. He adds that there was a problem with Google's Gmail back in September, but Google says that it's been fixed. Leo suspects it's more a local issue. Or it's possible that Louis's gmail account has been hacked. If he goes down to the activity link at the bottom right side, he can click on that and see if there's any nefarious activity going on. Leo also recommends looking at "All Mail" rather than any particular tab. Google has a technote on not getting mail as well.
Leo says it's important to know the difference between POP and IMAP mail. POP3 (post office protocol) is designed to use the server as a temporary storage place and it deletes them once he downloads his email. IMAP downloads a copy of the mail and leaves it on the server. Leo advises if he's using Gmail, he can disable POP so it doesn't delete his email from the server.