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.
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
Check for the latest database updates
First check if your F-Secure security program is using the latest updates, then try scanning the file again.
Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note: You need administrative rights to change the settings.
Detailed descriptions of Mimail variants are available in separate documents:
https://www.f-secure.com/v-descs/mimail.shtml
https://www.f-secure.com/v-descs/mimail_c.shtml
https://www.f-secure.com/v-descs/mimail_d.shtml
https://www.f-secure.com/v-descs/mimail_e.shtml
https://www.f-secure.com/v-descs/mimail_f.shtml
https://www.f-secure.com/v-descs/mimail_g.shtml
https://www.f-secure.com/v-descs/mimail_h.shtml
https://www.f-secure.com/v-descs/mimail_i.shtml
https://www.f-secure.com/v-descs/mimail_j.shtml