Robert,
I
don't know what STMP is, but I have a user who claims that
Groups.io does not, but? needs to, support his STMP alias of {redacted}.
If he's looking for the equivalent of an
Alternate Posting Address in Yahoo Groups, then he can add it to
his Groups.io Account page. He should click on his name in the
upper right corner of a Groups.io page (when logged in to his
primary address) and in the drop-menu select Account.
At the bottom of the page is a section for Advanced Settings For
Email Aliases:

If he's looking for the ability to use a single login account with
groups having different subscribed addresses then he's out of luck
- Groups.io doesn't support that (yet?) nor is there a way to move
subscriptions from one account to another nor to merge accounts.
If he means something else then we're going to need clarification
on what he's talking about.
Shal
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