Easy to use catch all email address

[daniel-naegele]

Use case

What problem you are trying to solve?
I would like to have a catch-all email address. This could be useful for example to use different email addresses for different websites e.g. amazon@example.org, github@example.org. This could prevent spam from single sites, as you could create another account after you receive too much emails from one service.

Your idea for a solution

Either via the maddyctl: maddyctl creds create *@example.org
Or the configuration file, where you could choose between different policies like reject or catch-all *@example.org

• I'm willing to help with the implementation

[foxcpp]

Probably not exactly "easy" but there is a way already using destination_in and address rewriting, described in maddy-storage(5). There is a typo in config example though... That needs to be fixed.

destination_in &local_mailboxes {
    deliver_to &local_mailboxes
}
destination example.org {
    modify {
        replace_rcpt regexp ".*" "catchall@example.org"
    }
    deliver_to &local_mailboxes
}

The logic in this configuration snippet is as follows: destination_in takes priority over destination, imapsql module can be used with destination_in acting as a list of existing IMAP accounts and modify block with replace_rcpt turns recipients for other addresses on a domain into catchall@example.org.

Note that I am not sure I want to make it easier since catch-alls are rarely a good idea - spammers frequently probe a lot of common addresses and you risk getting considerably more spam this way. Recommended approach for your use-case is to use prefixes with address rewriting, such as butzlabben+github@example.org being delivered to butzlabben@example.org. In fact, it is already implemented in default configuration: https://github.com/foxcpp/maddy/blob/master/maddy.conf#L102

[daniel-naegele]

Thank you for this extensively answer. Considering all the facts, I think I can close this issue now.

Keep up the good work.

[arisudesu]

The issue is a bit outdated, though it has to be mentioned that configuration above prevents delivering to correct local mailboxes when rcpt contains plus-tag.

E.g have local mailboxes catchall@example.com, personal@example.com. Mail sent to personal@example.com lands in personal@example.com mailbox as it should be, whereas personal+tag@example.com lands in catchall@example.com mailbox. Technically this is correct behavior, but it may not be common sense for everyone.

It may be resolved if modify {} block is applied before trying to deliver to destination_in:

# unchanged from defaults
table.chain local_rewrites {
    optional_step regexp "(.+)\+(.+)@(.+)" "$1@$3"
    optional_step static {
        entry postmaster postmaster@$(primary_domain)
    }
    optional_step file /etc/maddy/aliases
}

msgpipeline local_routing {
    modify {
        replace_rcpt &local_rewrites
    }

    # at this point rcpt was normalized to either:
    #       postmaster@$(primary_domain),
    #       local_mailbox_without_tag@$(local_domains),
    #       replacements with alias

    # destination_in block takes priority over destinations
    destination_in &local_mailboxes {
        deliver_to &local_mailboxes
    }

    # if rcpt is not in local_mailboxes, but has our domains,
    # replace rcpt to catchall and deliver it there
    destination $(local_domains) {
        modify {
            replace_rcpt regexp ".*" "catchall@$(primary_domain)"
        }
        deliver_to &local_mailboxes
    }

    default_destination {
        reject 550 5.1.1 "User doesn't exist"
    }
}

Now, mail sent to personal+tag@example.com lands in personal@example.com mailbox.

Should I be wrong, correct me, please.

[altdsoy]

Now, mail sent to personal+tag@example.com lands in personal@example.com mailbox.

Hello @arisudesu , is it possible to customize the "+ addressing" character?
E.g. I would like to use - instead of + which is often not recognized as valid on some websites.

I'm trying to self host a mail server for the exact same use case described here..
Come here from this link: https://vadosware.io/post/its-never-been-easier-or-harder-to-self-host-email/

I laughed when I read "You don’t have to postfix + dovecot in 2022.".

Hopefully I'll be able to start my self hosting email journey with maddy :)

[taoso]

Hi @altdsoy this is the default local rewrite rules for incoming email.

table.chain local_rewrites {
    optional_step regexp "(.+)\+(.+)@(.+)" "$1@$3"
    optional_step static {
        entry postmaster postmaster@$(primary_domain)
    }
    optional_step file /etc/maddy/aliases
}

The second line of optional_step regexp "(.+)\+(.+)@(.+)" "$1@$3" means treating receiver address of foo+bar@example.com as foo@example.com. You can see the \+ in the regular expression.

If you prefer -, you may change the above line to optional_step regexp "(.+)-(.+)@(.+)" "$1@$3". So all emails sending to foo-bar@example.com will be delivered to foo@example.com.