Mail problem

Sorry if it's the wrong section for this, but couldn't think of where else to put it!

I have a friend running a new Dual Core iMac, and he is having 2 problems with his mail client.
The first is with it not displaying properly, just showing as weird numbers and text. I believe that this is a font conflict though, so I'm sure I can solve this, but any confirmation would be appreciated.
The second is more perplexing though. It has decided to duplicate any Draft letter, or sent mail, in the drafts folder, sometimes up to 40 times for the same letter! I have no idea why it would do this - not something I can find any info on.
Any help with this greatly appreciated.
I had thought of trashing the plist file, to see if this helped.Anyone think it would work? It has solved other problems in the past.
Thanks in advance.

This duplication of drafts is happening to me also. I'm not getting as many copies as you though.

I have seen this problem mentioned when I googled it.

To me, this is a new problem, only in the past 3 weeks. I just delete the drafts that show up after I've sent the message.

I trashed my plist once and lost all my emails. It's a good idea to back them up first.

Thanks. For some reason he can't delete the drafts, but I probably need to look at it personally - he isn't the brightest spark!
I told him to back up the mails too.
As it's only the last 3 weeks, I wonder if it's a 10.4.9 bug.
All further comments still welcome.