I have had that happen that problem. For me it appeared to a bad e-mail message. I found that it would alway bomb out on that message. i was lucky it was part of my junk mail, so I could delete it to get around the problem.
If you have not done it in a while, you might want to try repair permissions. I hate to preaching it, but it resolve most problems.
Thanks, I found that it was a faulty mail preferences file in the Library folder. I found a fix on another site, to move this file for a test and it fixed it.
Shop for your Apple, Mac, iPhone and other computer products on Amazon.
We are a participant in the Amazon Services LLC Associates Program, an affiliate program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.