Mail endlessly "spinning" and terminating problem

Greetings!

I have suddenly this strange problem: Mail INbox on my MBP keeps showing activity (spinning indicator) and does not seem to complete bringing in all IN mail from YESTERDAY (today's mail seems to be OK).
Also, as I am looking at my MobileMe Mail folders online - to compare with my Mail folders on my MBP - I see that some SENT messages on my MBP from yesterday (today's seem to be working OK) do not appear in the SENT folder on MobMe, while some INbox messages on my MobMe IN folder from yesterday (today's seem to be OK) do not show up in my INbox folder on my MBP. I have tried repeatedly to sync btw MobMe and my MBP, no change,
MEANWHILE, as "spinning" continues re: my MBP's INbox, it all eventually ends with a window appearing stating:

+"Some actions taken while the account "myaccountname@mac.com" was offline couls not be completed online. Mail has undone some actions on some messages so that you can redo the actions while online. Mail has saved other messages in mailbox "Drafts myaccountname@mac.com" in "On My Mac" so that you can complete the action while online. Additional information: the connection to the server "mail.mac.com" on port 143 timed out"+

Then Mail simply quits operating. It's as if some "buffer" stored info is not getting "flushed out", preventing proper operation of remaining Mail functions.

I am aware that at some point YESTERDAY, I did experience some pb with sending a few emails with photos attached. i still not sure that they got to their destination. I might also have manipulated those messages offline indeed.

It seems that Mail is currently caught up in a never ending spin, seemingly preventing proper operation of the Mail system altogether, especially re: YESTERDAY Mail activity. I do not know if my description all makes sense, but I do wonder if and how - for starters! - i can end INBox "spinning".

Attachments show Inbox/myaccount constant "spinning" and eventual error window. Also, communication btw my iPhone, MBP and MMe account

Thank you for any advice!

- Roger T