NAV SMTP transport error

Hi Friends,

Im running a NAV 2 services setup. In one of them I get the following error:



I have been reading, trying to compare service settings.... the funny thing is when you restart service it works again, for some time.

-Does any1 know what could be?
-As a workaround is there any way to run another NAV service codeunit from code (I know sounds strange)?

many thanks.