At doschranky.cz, we allow to send text you want to have printed on a postcard with e-mail. It did not look like a problem, until somebody got postcard with message: "Scanned with AVG, 0 viruses found."
The system is fully automatic, but now it looks like we will have to check all texts by hand. Antivirus software and some free emails adds various text at the end of each email.
I am trying to figure out, how to discover text not added by user, but manual check will be the best fix at least for now.