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.
Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.
More information on the 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: