Convert text file to mbox file?

[Dr. C. Baxter]

Hello,

In my rmail configuration, I have sent the variable
'mail-archive-file-name' to a local file 'sent'. All appeared to go well
for several months, but when I now try to read 'sent' via "M-x rmail-input"
I'm told that 'sent' is an Invalid mbox file. I think the problem may
have arisen when I edited and saved 'sent' as if it were an ordinary
text file. Is there anyway in which I can covert 'sent' back to an mbox
file?

Thanks.

Best wishes,

Colin Baxter.