One specific account on my RaQ4i is receiving the following error when trying to check their email:

Log In Error: -ERR [SYS/PERM] Unable to process From lines (envelopes), change recognition modes or check for corrupted mail drop.

This started recently after a server crash and manual reboot. Everyone else's account seems to be fine. I tried contacting tech support who said everything seems to be working fine and dubbed it a DNS issue, which is out of their scope. I know it's not a DNS issue since it was working fine previously. Any ideas?

Can you remove the user and readd them?

Well I could but they would loose all email sent to them so far. Is there any way to restore the email they've received?

I was able to fix this problem by first backing up the mail spool file in /home/spool/mail, then deleting the useraccount, recreating the useraccount and restoring the mail spool file to /home/spool/mail. This fixed what ever was corrupted and the user was able to download his mail that had been piling up.