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Exim mailalias/announce

Sometimes it's useful to be able to set up outgoing mail aliases to send out announcements or reach a limited group of people -- similar to a closed majordomo or mailman mailing list.

But if only need a really cut down version just to send the odd announcement and you don't fancy installing any additional software just for that purpose, you might just do it with Exim. The version I am using is fairly easy to set up and uses SQLite for the member management.

> Exim Main Configuration Settings

domainlist mailalias_domains = sqlite;/etc/mail/mailalias.db \
		SELECT DISTINCT domain FROM forward \
		WHERE domain='${quote_sqlite:${domain}}'
domainlist local_domains = +mailalias_domains : \
		+user_domains

The local_domains shown here is just an example an will differ from your local configuration -- you just need to make sure to add +mailalias_domains to the local_domains domainlist.

> Exim mailalias Router

mailalias:
  debug_print = "R: mailalias for $local_part@$domain"
  driver = redirect
  domains = +mailalias_domains
  no_check_local_user
  senders = ${lookup sqlite {/etc/mail/mailalias.db \
			     SELECT sender FROM sender \
			     WHERE local_part='${quote_sqlite:${local_part}}' \
			     AND domain='${quote_sqlite:${domain}}'}}
  condition = ${if and {\
		{or {{match_ip{$sender_host_address}{+relay_from_hosts}} \
		     {!eq{$authenticated_id}{}}}} \
		{!match{$header_x-loop-detect:}{^<${local_part}@${rxquote:${domain}}>\$}}}}
  headers_add = "X-Loop-Detect: <${local_part}@${domain}>"
  data = ${lookup sqlite {/etc/mail/mailalias.db \
			  SELECT recipient FROM forward \
			  WHERE local_part='${quote_sqlite:${local_part}}' \
			  AND domain='${quote_sqlite:${domain}}'}}
  forbid_file
  forbid_include
  forbid_pipe
  retry_use_local_part

mailalias_fail:
  driver = redirect
  domains = +mailalias_domains
  data = ":fail: ${if match{$header_x-loop-detect:}{^<${local_part}@${rxquote:${domain}}>\$} \
		   {Mail loop detected}{Invalid address}}"
  allow_fail
  no_more

Note that the condition in the mailalias router is very restrictive to avoid any forged posts to the mailing list from the outside (but you might want to adapt that to your local requirements).

And finally, we need to set up the database to actually create our announcement mailing lists.

> Database Schema for /etc/mail/mailalias.db

CREATE TABLE forward (id INTEGER PRIMARY KEY, local_part TEXT NOT NULL,
    domain TEXT NOT NULL, recipient TEXT NOT NULL);
CREATE TABLE sender (id INTEGER PRIMARY KEY, local_part TEXT NOT NULL,
    domain TEXT NOT NULL, sender TEXT NOT NULL);
CREATE INDEX forward_address ON forward (local_part, domain);
CREATE INDEX forward_domain ON forward (domain);
CREATE INDEX sender_address ON forward (local_part, domain);

To create a test@announce.example.com mailing list we can then use the following SQL statements to populate the database.

> Sample /etc/mail/mailalias.db

INSERT INTO forward (local_part, domain, recipient) VALUES
  ('test', 'announce.example.com', 'user1@example.com');
INSERT INTO forward (local_part, domain, recipient) VALUES
  ('test', 'announce.example.com', 'user2@example.com');
INSERT INTO sender (local_part, domain, sender) VALUES
  ('test', 'announce.example.com', 'sender@example.com');