Have you added the primary account as an allowed sender in gmail settings (see picture)? Is the primary account set in TB to send on the gmail smtp (smtp.gmail.com, 465, SSL/TLS, OAuth2, email address)?

Person created another question with answer - https://support.mozilla.org/en-US/questions/1465274

I've asked them to keep info in this original question. Here is the content

Hi there it's Ray Hurley again. I received your response on my cell phone and tried to respond but it didnt work. So to answer your questions No I have made Gmail smtp the default sender Other thing is as expected Gmail sends no problem,but my primary account won't Yes the settings you sent me are exactly what I have.

Have you set it up in gmail webmail account to allow sending using a different email address.

https://support.google.com/mail/answer/22370?hl=en-GB

Yes Ive followed the set up instructions as in "Add an address that yoiu own" I get as far as

Add another email address you own Send mail through your SMTP server Configure your mail to be sent through telkomsa.net SMTP servers Learn more SMTP Server: smtp.telkomsa.net Port:465 Username: ray@telkomsa.net Password: Secured connection using SSL (recommended) Secured connection using TLS

	Couldn't reach server. Please double-check the server and port number.

I've checked and double checked server and port number, what else can I do

I'm somewhat confused by the method suggested above, as it doesn't work like I thought it did (or should). Fortunately, there is another method that might be adequate.

I selected the gmail account in Account Settings, then Manage Identities in the right pane, Add..., on the Settings tab, entered Your Name, the non-gmail address in Email Address and Reply-to Address, selected the gmail smtp under Outgoing Server (SMTP), entered a distinct Identity Label. On the Copies & Folders tab, for 'Place a copy in' selected the non-gmail Sent folder (or could set a folder under Local Folders). Kept other folder targets the same.

When composing a new message, select the new identity in the From drop-down. Recipients will see the message as if it was sent from the gmail address, but will reply to the non-gmail address.

I'll look for a better solution that hides the gmail address.

sfhowes, I will be eternally grateful for your help, support, patience and diligence in helping me solve this most frustrating of issues. I tried the new setup instructions you sent and even though I was not completely sure what I was doing, my email is working like a dream. You spoke about another possibility which I'd like to hear about (a sort of backup idea if you like) The only thing I wish we could avoid is having to change is when sending having to ensure the gmail address is used in the From drop-down list.

Many, many thanks once again. Look forward to hearing from you.

I haven't figured out the gmail labelling issue, but the method is probably simpler by ignoring identities and just selecting the gmail smtp in the non-gmail account settings and entering the non-gmail address in the Reply-to box.