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starbeamrainbowlabs
Asked: 2017-06-17 12:27:09 +0800 CST

Postfix + Dovecot: Create send-only email account

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I've got a nice little mail server setup (running Ubuntu Server 16.04) that works a treat. It uses postfix as SMTP, which uses dovecot (IMAP) as an authentication source for virtual mailbox users.

It's been working fine, but now I have a second server in another location (with a dynamic IP address), which I'd like to be able to send mail through my main mail server. I've seen a guide on setting it up in authenticated-relay mode, and am part-way through the process, but then I realised that I'd need a send-only email account for it to authenticate against, as I don't want it to be able to receive mail and fill up the server's hard drive (I won't check the inbox!).

How can I create a new email account in my virtual users setup that doesn't have a mailbox, but can still connect via SMTP and send emails?

linux

1 Answers

  1. Best Answer

    The easiest solution would be to add the user just like any other user, but restrict recipient. This will give an error during RCPT TO regardless whether the user actually exists or not.

    For example, if a web page of a company might send some emails using [email protected] as a sender address, while no-one should read that address but only their [email protected] addresses, and the server has mydestination = example.com that would normally deliver to that user, I'd simply add (without removing what there already is in smtpd_recipient_restrictions):

    smtpd_recipient_restrictions =
    . . .
    check_recipient_access hash:/etc/postfix/access/denied_recipients,
    . . .

    check_recipient_access type:table

    Search the specified access(5) database for the resolved RCPT TO address, domain, parent domains, or localpart@, and execute the corresponding action.

    Then add the unallowed addresses there with a friendly and human readable reason for the reject:

    [email protected]    REJECT    Visit the web site for correct contact information.
[email protected]   REJECT    Please log in and use the helpdesk contact form.

    That should work what ever is the reason you don't want to accept mail for an address. Remember to postmap /etc/postfix/access/denied_recipients as the lookup table is a hash type Berkeley DB.

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