Using gmail to send as another domain's email address
 

For many years I have used gmail both to collect e-mail sent to another address I own and to send email as if it were that address. This matters because the other address is simply a forwarder (so it has no mailbox of its own) and I prefer not to expose my gmail address when replying or initiating a new e-mail; nothing dodgy in the slightest, just that to "send from" the other address is more professional and associates it with a website of the same domain.

By definition of the other address only being a forwarder it has no login. I cannot log in to smtp.the_provider.com - only to the account that administrates this (and many other) forwarders. This means that to send e-mail appearing as if it is this account I need to use another provider's smtp server - and I chose smtp.gmail.com as it was the only one that was free and worked every single time I tried, anywhere in the world and without irritating me that 10 minutes ago I appeared to be in another continent (but all I have done is move buildings and changed to an internet connection that happens to be a VPN tunnel to a different continent).

Some months ago, Google clearly changed something because out of the blue all e-mails I tried to send this way from both the web client and Gmail app on my smartphone and tablet started to fail with a message that can be summarised as "the relay smtp.gmail.com rejected your login" - even though the credentials are correct and I have already verified that I own the non-gmail account I am pretending to be.

Inference is that I can no longer use smtp.gmail.com as a free and convenient mechanism to send non-gmail even though the setup process (which as mentioned includes verifying that I own the other account, as well as logging in to my gmail account with smtp.gmail.com set as my smtp server) works fine. This applies whether I do it as an alias or not.

Before I give in has any other PPRuNer solved this challenge in a way that can be described, please?

Interestingly I can still do as I wish when using eM Client on my laptop but this is not always an option.

TVM,
TLXV

These days there's every chance your spoofed e-mail will be marked as spam or rejected due to the sender address not being linked to Google.

That's what I'd have thought too, le Pingouin but mail sent as the same "from" address via eM Client (the email application I run on my laptop and which also uses gmail as the SMTP server) has never - not even once - been rejected by the relay or bounced further down the line and I have never had anyone say they didn't receive what I sent or had it arrive marked as junk.

It is most odd that I can do this as described via laptop client yet not via Gmail web or Android app. Currently, the Gmail option to "send as" is as much use as a chocolate teapot in either of the latter two scenarios.