How To Send Using An Alias Via SMTP?
Question asked by Jeff Rueckgauer - 3/25/2022 at 6:18 AM
How do you configure Outlook or the Windows 10 mail client to send mail using an alias using SMTP? I have the alias set to "can be used as a from address in webmail." I'm getting a 550 error "From address must match authenticated address." 

We're migrating from Google's Workspace which doesn't have a problem with this. DItto for Exchange/365. I would rather not have to create a bunch of individual mailboxes to accomplish this.

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Tony Scholz Replied
Employee Post Marked As Answer
Hello Jeff, 

Currently the send as an alias option is only available from webmail, and only for members of that alias. 

  • Alias can be used as from address in webmail - Enable this option to allow alias users (those users/accounts that are part of the alias) to manually change their From address to the alias email address on new emails and replies. When a user sends mail as an alias, the recipient will see the alias's Display Name as the email friendly from address. If the Display Name for the alias is blank, the user's Display Name shows.
Thank you
Tony Scholz
System/Network Administrator
SmarterTools Inc.
(877) 357-6278
Jeff Rueckgauer Replied

Thanks. I figured as much but I figured I check since there could be buried treasures.

Any plans to add the ability to use an alias to send via SMTP? From a programming standpoint it should be relatively easy: The auth is using the mailbox credentials and that needn't change. If the Message From Name != Mailbox and From Name != (one of the aliases the mailbox is associated with) then reject the message. Otherwise, go ahead and send it. 

This makes a lot of sense where you have multiple recipients for an alias within the same domain being able to respond as the alias instead of their individual identity. For example, Tony and Jeff receive for "support@dev.nul". Management may have software intercepting the mail to log and track progress, the communication log. Customers going directly to tony or jeff @dev.nul would break that process.

On a related note, how about adopting the Exchange and Google pattern for assigning aliases to the mailbox/user and calling the existing pattern a list or group?

Zach Sylvester Replied
Employee Post
Hey Jeff, 

I just wanted to follow up on this thread. Technically you can send via the alias from a client using SMTP. But you have to disable SMTP authentication via IP whitelisting. 
Heres an example of a script that I made that uses SMTP. 

You can whitelist the IP address for SMTP authentication bypass in Settings->Security->Whitelisting

Please let me me know if this helps. 

Kind Regards, 

Zach Sylvester

System/Network Administrator
SmarterTools Inc.
(877) 357-6278

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