Mimail is a family of simple mass-mailing worms which send various messages with infected EXE or ZIP attachments.
Some of the variants contain payloads such as stealing credit card information or Distributed Denial-of-Service attack against certain website.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for more information.
Detailed descriptions of Mimail variants are available in separate documents: