Suddenly I am having this very weird problem. When I try to email an invoice, i get this error:
https://www.dropbox.com/s/ppmbp6v02gwsrpg/Screenshot%202014-01-06%2009.01.55.png
My email communication is turned on. I know when I put email communication off, I get errors like this 'This Letter cannot be send', which is normal because I turned them off.
It's very strange, I didn't make any modifications to the system and suddenly some emails wont send automatically. (or I did change something but I don't remember what?)
Can somebody help me with this problem? Thanx in advance