NPrinting:error while sending a message(Unable to relay)

[Anonymous]

Hi gurus,

I'm using Nprinting designer version15.3. and Nprinting server version 16.0.

Everything was running perfectly till several days ago. Nprinting started failing to  distribute emails. The error I got is

" Error while sending a message (Unable to relay)".   It is quite wearied, since it just happened like a click. I suspect it may be regarding to SMTP settings.  But I sent test E_Email from Nprinting e-mail settings and it worked.

Please anyone could help me.