Well there is good news and bad news. For the past three years I was with AOL, using there own email facility without problem. Early this year I tried a different dial-up provider for two weeks, [Freeserve]
I had exactly the same problem with express. Neither Freeserve or Microsoft could pinpoint the problem. But it happened less if I closed down my anti-virus checker. [AVG] As you will see from the link above provided by VoG, the common link in all cases seemed to be Freeserve and or AVG.
Because of this annoying problem I went back to AOL. Last week I changed to zen Broadband, firmly under the impression that I would have this problem recur, but not worried too much as I would use "Outlook" instead, as this program is not affected.
To my complete surprise and delight the problem is not there and I can use express without any problems at all. There are many users of express having this problem and a search through google will bring up suggestions on how to fix, but none seem to work in all situations.
Sorry I can't be of more help, I realise this is a very annoying problem and wish you luck in finding the answer. j.
As I mentioned in my post above, there are many attempts to fix this problem. I have just done another search and come across this answer. I have no way of verifying if it works, but you could do a search of all your mail and check for any without a subject heading, delete these and re-boot, then test by sending e-mails to yourself. j
The problem is caused by an email in your Inbox which has a sender but NO subject. Try saving that message somewhere, then deleting it. Worked for me. Yes m$ has a fix, but their advice is to contact them for support costs rather than a link to download it.