replace_rcpt for outgoing email

[Nairou]

Apologies for bringing this up again. I'm trying to apply the change you mentioned in #419, but am uncertain exactly how the replace_rcpt line should be integrated into the local_rewrites section. Every attempt I've made so far gives an invalid config.

[nickersonm]

If you put it in local_rewrites, then in the authorize_sender section the 'from' address will be transformed according to the regexp rule before checking if it's a valid sender. See the examples here, or alternatively use a database query as shown here.

[Nairou]

Thanks for the response. My confusion is what else I need to put in local_rewrites for it to accept the replace_rcpt line.

This is my current local_rewrites:

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

If I drop a replace_rcpt regexp ".*" "[email protected]" within that block at the end, I get an error trying to restart the server. I also tried wrapping it in a modify{} block, but still got an error.

[nickersonm]

Note that local_rewrites is a table chain that's (by default) already used in a replace_rcpt, e.g. replace_rcpt &local_rewrites. You don't want replace_rcpt for sender address authorization, you are dealing with the prepare_email directive instead. So what you want to do here is either:

• Add a new optional_step to the end of the local_rewrites chain that transforms whatever's left to the catchall address, in which case the catchall address will also receive unaddressed emails
• Make a new table.chain to use with prepare_email that includes both local_rewrites and the catchall regexp steps

In either case the directive will be checking the address coming out of the table transformation against the logged in user.

I do something similar, albeit more complicated, using:

# Local address rewriting
table.chain local_rewrites {
  # Plus-address rewriting
  optional_step regexp "(.+)\+(.+)@(.+)" "$1@$3"
  
  # Defined aliases
  optional_step sql_query {
    driver sqlite3
    dsn smtp.db
    init "CREATE TABLE IF NOT EXISTS alias (source_like TEXT, source_glob TEXT, notsource TEXT, destination TEXT NOT NULL)"
    lookup "SELECT DISTINCT destination FROM alias WHERE (:key LIKE source_like OR :key GLOB source_glob) AND destination NOT IN (SELECT destination FROM alias WHERE :key GLOB notsource)"
  }
  
  step identity
}

# Allowed sending aliases
#   "domain" for any address at specified domain
#   "*" for any address at all
#   "email@domain" for specific alternate address
table.chain sendalias {
  optional_step sql_query {
    driver sqlite3
    dsn smtp.db
    init "CREATE TABLE IF NOT EXISTS sendalias (address TEXT PRIMARY KEY NOT NULL, alias TEXT NOT NULL)"
    lookup "SELECT DISTINCT alias FROM sendalias WHERE :key LIKE address"
  }
  
  step identity
}

...

# SMTP user submission server
submission tls://0.0.0.0:465 tcp://0.0.0.0:587 {
  
  ...
  
  # Process local domains
  source $(local_domains) {
    # Check that sender is authorized
    check {
      authorize_sender {
        prepare_email &local_rewrites
        user_to_email &sendalias
      }
    }
    
    ...
}

[Nairou]

Thank you VERY much for your help! I got the first option (add a new optional_step to the end of the local_rewrites chain) to work, and that's good enough for me, as I'm the only user on this email server. I don't know if that will bite me later, or if the config will still route to/from real addresses before the catchall.

I really wish the config made sense to me, I couldn't for the life of me get the second option to work. I don't use a SQL database, so couldn't follow your example too closely. But, I have it working well enough now, so thank you!

[nickersonm]

You're welcome! If you want to explore the configuration more, I suggest going through all the documentation a few times and also translating how you think the default configuration works. I found it helpful to rebuild the default configuration starting from scratch and adding a few lines at the time while observing behavior with maddy run --debug.