Level 2

I use tpg just for email.  Most of time its OK but I recently have not received an email and the sender claims they sent it.  On looking on TPG website and my post office there, the email is sitting there but for some reason has not been downloaded to me when my send/receive process has been activated.  surrounding emails have all been downloaded OK.  This may not be an isolated case as something similar may have occurred in the past.  Any ideas