MAIL not receiving some email

I am not receiving email from only certain Senders. From what I can tell, this started several months ago. I have the additional complication of having an AOL account as well as a .Me account accessed thru MAIL. BOTH are experiencing email loss from only certain senders. One of those is my wife who has the same MAC BOOK PRO, same version of Snow Leopard, and same set up for an AOL account accessed thru MAIL, thru the same ISP.

My MAIL Connection Dr shows BOTH accounts with a red dot stating LOG in to SMTP acct failed- Verify user name and Password, which coincidentally is the same notice I get from MAIL periodically. As far as I know, it is all correct, and I would assume, if it were NOT, I would not get ANY mail.

Anyone have any ideas? This whole SMTP and IMAP concept has me stumped, though I don't know if it is related to this. My MAIL vesion is 4.6.