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I'm very new to Exchange (in fact, an apprentice and studying it at the moment) and am wondering how the Postmaster@domain.com address works. An example:

A smarthost configured with one mailbox, Postmaster@serverfault.com, with an *@serverfault.com alias so, my understanding, all mail sent to *@serverfault.com is SMTP forwarded onto the postmaster@serverfault.com address.

But what happens now? Does Exchange have a master mailbox Postmaster, that receives all this mail and just dishes it out to the correct mailbox? Or is what I just wrote a pile of garbage!

So I'm a little confused. On the Smart Host - there is SMTP forwarding to forward all SMTP to IP Address x.x.x.x which is active for a mailbox on the smarthost called Postmaster@domain.co.uk with an alias of *@domain.co.uk? How is this working exactly?

Thanks!

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1 Answer 1

The postmaster address is an RFC mandated specification. Essentially every e-mail domain on the planet should have one as a best practice. Typically the e-mail that is received at this address is sent or shared with the mailserver administrator.

Typically Exchange forwards all postmaster e-mail to whatever address is setup as the server administrator. In addition as you pointed out the wildcard prefix is indeed a catch all e-mail address. This means that all e-mail is received by default regardless of whether or not the mailbox exists or not. You may or may not want to disable this so that e-mail sent to the wrong user is rejected (a.k.a. Bounced).

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Sorry - but how then does it work exactly - if all my mail is being forwarded by the smarthost to postmaster? –  PnP Sep 4 '12 at 19:03
    
The address is provided so people outside of your domain can send an email to the postmaster, like you have a user who is spamming me, etc. although abuse@ is normally reserved for that. If you have a real mailbox defined mail will be delivered to the mailbox, the *@domain is only used if no matching mailbox is found. –  Brent Pabst Sep 4 '12 at 19:06
    
So I'm a little confused. On the Smart Host - there is SMTP forwarding to forward all SMTP to IP Address x.x.x.x which is active for a mailbox on the smarthost called Postmaster@domain.co.uk with an alias of *@domain.co.uk? How is this working exactly? –  PnP Sep 4 '12 at 19:09
    
You're getting to the point where you need to grab a book or other resource. You have asked about three or four different topics that would be found in a typical Exchange Admin book. –  Brent Pabst Sep 4 '12 at 19:12
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It's not just best practice. The postmaster address is mandatory, i.e. every MTA MUST provide a postmaster address to be compliant. –  Ansgar Wiechers Sep 4 '12 at 19:57

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