Receiving error when attempting to send AR invoices via SMTP:

Error occurred while processing email.  For more information about the error, run the Document Transmittal Log from the CI Reports menu.

Right.  The log says "Unable to send message".  

One of my questions is that other applications we use that interface with email (Knowledgesync and TaskCentre) provide authentication for the sending email account.    I see nowhere in Sage 500 to provide a password.

I have setup

1. Doc Transmittal in CI options, using SMTP server name and defined a specific port (smtp.comcast.net:587)
2. The invoice with subject, Body and return address in Set up Document Transmittal in CI
3. Customer email address as my own, defining an invoice to be sent by HTML (get same results if I choose RTF and PDF)

I have tried this on my own machine, and I've tried using the client's SMTP server  on their machine, as well as smtp.google.com.  All with the same results.

I've opened the outgoing ports in the firewall.

I read in an earlier post that google mail is not supported.  Is that still the case?

Sage versions range from 7.3 to 2016.

On the 2016 version, I get an additional Report Engine error:  ProcessReport - -2147206398:Memory full.  Thought this might be an issue with the form, but if I attempt a print, without engaging document transmittal, the error does not occur. 

Thanks to anyone that can help.