Hi,
I am using SpamAssassin to detect spam mails, and use procmail to redirect the detected spam mails to a separate folder.
Now I want to automate a task which will delete the spam mails (sendmail format) in the mail/spam file of every users home directory and send a warning before 7 days of deletion.

How is this possible?

regards
Krishna

One idea would be to have spam delivered to people's mailbox in the
/home/${LOGNAME}/mail/spam.${WEEKNUMBER} format.
(and maybe link that to /home/${LOGNAME}/mail/spam if users are accustomed to having the mailbox called like that)
Then you could set up procmail to test for an existing /home/${LOGNAME}/mail/spam.${WEEKNUMBER}. If it is a new week the mailbox would not exist, archive the old one, make one, link one, fire off a message at ${LOGNAME} and finally delete the folder that's date --date='2 weeks ago'.

If you don't want to burden the procmail processes with this you could trigger a script easily.