A program that does not fall into any other category.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
F-Secure Anti-Virus can detect certain compressed/archive files that have a big compression ratio (for example 1 megabyte archive or compressed file that expands into tens of megabytes of data) as 'Mail Bomb'.
This does not mean that any infection was found in those files, it's just a warning.
If you have a file detected as Mail Bomb, please exclude it from scanning for both On-Access and On-Demand scanners of your F-Secure Anti-Virus.