mail problems debian

[Keith Barrett]

Firstly, sorry for putting this on the list but am going round in circles and not 
getting anywhere.

I have a couple of email addresses and what I am trying to do is use 
fetchmail to pick up all the mail from the various addresses and use 
procmail to sort in to various maildir's.

I did get mail collected from the isp with fetchmail but was finding that the 
mailbox seemed to be getting corrupted on a regular basis and mutt 
reported
/var/mail/keith is not a mailbox.

If I deleted the file /var/mail/keith and created a new empty one, mutt would 
open and report no mail, as expected but as soon as any mail was 
downloaded, mutt would not open that mailbox.

I could still read the file outside of mutt but that was not ideal.

I thought maybe some of the headers from some list may have been a 
problem so thought to use maildir instead.

Now, if I have the line
mda "procmail -f-"
in the .fetchmailrc fetchmail gives an error.

>From googling, some results suggest I need a .forward file in my home 
directory but this was not conclusive.

Any thoughts on the corrupted mailbox and the way to go would be good.  
Do I need to change the .procmailrc to use maildir?  Is using maildir likely 
to reduce the corruption?

Thanks

Keith