Lexmark CX510 scan to email settings

I am trying to get this working using my gmail account and smtp.gmail.com settings.
It worked until about two weeks ago but now I have the following error:

Connection failure: <-11>
Could not resolve the server address

Have tried various settings and ports 587, 465, 25 but get the same error every time.
Wondering if anyone has this working on their Lexmark printer.

Thanks