Note: This information may be completely wrong. I don’t speak this language, and this is just my best guess after doing a bit of online searching.
According to this Language Identifier site, the language seems to be Slovak.
I looked through a few dictionaries, and what the phrase seems to be saying is “Unsent file with virus”. I can’t find anything that defines"neposielajte" in its entirety, but “posielat” seems to be some variant of “send” (sending, sent, something like that), and the “ne” at the beginning of the word seems like the English “un” (like undying, unknown).
If that it’s correct, I’m guessing it’s the mail server telling you that the whatever was originally in the email wasn’t sent to you because there was a virus.
But I really don’t know. I hope a person who actually knows the language will come along and help you soon.