Had a user that would get a C018 error (database error) when he would attempt to reply to an external user's e-mail address. He was able to create a new e-mail to this e-mail address with no issue, it just seemed to be an issue when replying to this specific e-mail address. He was also able to reply to this external e-mail in webmail with no issue. I attemped mailbox repair and it did not resolve the issue. The user did not want to resort to the mailbox rebuild since it would unsort all of his e-mails, so he just chose to live with the problem instead. Issue closed ...sort of.

However, now I have another user with the exact same error with the exact same external e-mail address. It seemed odd/rare that two users would now have a database error that would involve the same e-mail address so is it possible that the cause could be the external e-mail address? Also, may not be related to the issue, but the second user also received a security certificate window when receiving the external e-mail. The email was in HTML but no links except some images in the external e-mail's signature.

Any ideas? Thanks.