sendmail and /home files

[Fred Martin_1]

I've noticed that, in the process of delivering email, sendmail temporarily writes out files in the recipient's home directory, in the form:

/home/fred/fred.23123

I assume the number is ID of the process spawned to handle the delivery. In any case, the file is removed after a few seconds, normally.

I have in the past however, discovered old files in user's homes. And, when /var fills up to 100% these files appear in abundance and are not removed, many of them identical, as (I'm guessing) sendmail keeps re-trying to deliver the mail.

Well, if /var is full then /home fills up too, under those conditions.

Does anyone else see this happen? And, what can be done to reduce the chances of a SPAM attack bringing my server down?

Some obvious things would be to limit the size of incoming emails, and have rather large disks for /var and /home. Any other ideas are welcome and if anyone knows the detail of what sendmail is actually doing with these 'temp' files, I'd like to hear it.