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Old 1 Oct 2021, 04:17 PM   #6
brong
The "e" in e-mail
 
Join Date: Jul 2004
Location: Melbourne, Australia
Posts: 2,696

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Fastmail.fm
Quote:
Originally Posted by BritTim View Post
Thank you for chiming in. This all seems reasonable, but there is an edge case that could be an issue.

Consider an alias for a colleague's account, where you are also allowed to send on behalf of that alias You both choose to have a wildcard sending identity of *@user1alias.fastmail.com. Now, this will not be an issue for user1, but I assume your plan is to forbid this for user2.
If it's within the same customer, then the alias is owned by the customer so it's fine. Otherwise... you'll have to create a specific sending identity and verify it. It's enough of an edge case that I'd be tempted to say "change how you're doing things. Maybe by setting up an "SMTP ONLY" app password and having user2 send authenticated back to fastmail as user1 when using that identity.
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