Can't send in game mail

Hello

I've got a problem with one alt char, can't send in game mail to this specific character, when i try to send mail it says "Cannot find mail recipient."
Every other alt mailing works fine. Anyone else had similiar problem? Any tip how to solve it?

all chars are within one account, same faction.

Thanks in advance

EDIT:
When at last, after 5 days of waiting the server was restarted everything was back to normal, now mailing works on all chars.