Shared Mailboxes and Postfix

Kevin P. Fleming kpfleming at
Mon May 9 11:25:54 EDT 2005

Josh Whitver wrote:

> As I understand it, this should allow us to send mail to "Conference+<shared
> mailbox name>@<domain>" and have the message delivered to the shared mailbox. 
> This isn't what's happening, however.  Initially, there was no mail-capable
> user named "Conference", so I created one, but now all mail sent to the address
> above gets delivered to the "Conference" user Inbox, not the shared mailbox.

I just went through this myself last week :-)

The Postfix 'local' process won't accept mail for users it can't 
identify, so it does not think there is a valid local recipient for 
'Conference' unless you add it as a user, which doesn't accomplish what 
you want.

Instead, you need to make two changes in your Postfix

First, add "recipient_delimiter = +", so that Postfix will ignore the 
"suffix" after the username when looking for a match.

Second, if you don't already have a 'local_recipient_maps" line, add one 
using the default contents (which are shown in the local(8) man page).

Third, create a file in your Postfix config directory called 
'shared_folders', with contents like this:

Conference yes

(the second token can be anything, it just has to be present). In the 
Postfix config directory, run "postmap hash:shared_folders" to create a 
hash db from this file. Finally, add 'hash:shared_folders" to the end of 
the local_recipient_maps line in and restart Postfix.

There is one downside to this configuration: Postfix will accept mail 
addressed to Conference+<anything>, then Cyrus will reject it if there 
is no matching folder. If you wish, you can list each valid shared 
folder in the shared_folders file, and don't add the 
'recipient_delimiter' option to, which will avoid this problem 
but require more maintenance as you add/remove folders.
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