Mailbox Rebuild

I haven't been receiving email messages on my iMac (OS X Lion).

I've checked all settings and everything seems to be OK. I finally discovered the "rebuild" feature for the mailbox, and this brings all my emails into my inbox.

My question...Is there still a setting I am missing? Why won't the messages come into the mailbox unless I do the rebuild?

Just seems like I shouldn't have to do this extra step???

Still learning the basics on my new iMac.
Thanks

You didn't tell us who your ISP is but try removing the account from Mail and set it up again. Make sure all the information you enter is correct... server addresses, passwords, etc.

I have both yahoo and gmail. Both behave the same.

Guess as long as I can get my mail, I should be satisfied. But I will try your suggestion.

Thanks!