Problem: Antivirus software detects a virus in incoming mail, quarantines the file in which the virus resides.
Mailer hangs or other kinds of confusion may occur when trying to access the quarantined (or deleted) file.
The quarantined file may contain all messages in a box/folder. Thus, allowing antivirus software to delete it may delete all of the users inbox, or at least everything just downloaded.
Depending on mailer settings and behavior, allowing antivirus to delete quarantined files may result in deletion of mail from the server as well, eliminating the possibility of working around the problem and retrieving the rest of the mail.
Un-quarantine the file, delete the offending message immediately without viewing or previewing it. Not recommended for Outlook users.
For those with accounts on our mail systems, log in and use pine to delete the offending message. But see complications above.
If preview is enabled in the mailer, the malware may get executed, infecting the system.
Mailer bugs may (have in the past, especially Outlook) allow the malware to get executed even if preview is turned off.
This would all work better if antivirus software properly understood mail. Catching viruses at the "write mail to disk" stage and treating them as files interacts badly with mailers.