Not getting email sometimes in Mail in Leopard

[brainwave89]

I view my comcast.net email on a PC (not for long) and my 4 month iMac using Mail. There have a been a few instances that I have noticed that email that shows up on my PC will not appear on my iMac. I would say ten times. There is nothing consistent about this behavior that I can notice.

Any suggestions on why this happens? Both accounts are set to leave messages on the server after retrieval.

 

[tibi08]

The only times I've had this have been using gmail where I send an email to myself. For some reason that causes an issue either with gmail or Mail.app