Add workaround for blocked incoming port 25 to Postfix post.

Also convert tabs to spaces.

diff --git a/posts/Postfix.mdwn b/posts/Postfix.mdwn
index 8407ce2e2c311e194eb2d74f81821b641eecae1e..e1fafaf0abfefb0c7c7132c56554bb6417ef0f31 100644 (file)
--- a/posts/Postfix.mdwn
+++ b/posts/Postfix.mdwn
@@ -1,9 +1,14 @@
 I spent some time today configuring [Postfix][] so I could send mail
-from home via [[SMTPS|STMP]].  Verizon, our ISP, blocks port 25 to
-external domains, forcing all outgoing mail through their
-`outgoing.verizon.net` exchange server.  In order to accept mail, they
-also require you authenticate with your Verizon username and password,
-so I wanted to use an encrypted connection.
+from home via [[SMTPS|STMP]].
+
+Outgoing mail
+=============
+
+Verizon, our ISP, blocks port 25 to external domains, forcing all
+outgoing mail through their `outgoing.verizon.net` exchange server.
+In order to accept mail, they also require you authenticate with your
+Verizon username and password, so I wanted to use an encrypted
+connection.
 
 For the purpose of this example, our Verizon username is `jdoe`, our
 Verizon password is `YOURPASS`, you're running a local Postfix server
@@ -18,14 +23,14 @@ free local port.
     sender_canonical_maps = hash:/etc/postfix/sender_canonical
     # cat /etc/postfix/saslpass
     [127.0.0.1]:12345 jdoe@verizon.net:YOURPASS
-               # postmap /etc/postfix/saslpass
-               # cat /etc/postfix/sender_canonical
-               root@mail.example.com jdoe@example.com
+    # postmap /etc/postfix/saslpass
+    # cat /etc/postfix/sender_canonical
+    root@mail.example.com jdoe@example.com
     root@example.com jdoe@example.com
     root@localhost jdoe@example.com
     jdoe@mail.example.com jdoe@example.com
     jdoe@localhost jdoe@example.com
-               # postmap /etc/postfix/sender_canonical
+    # postmap /etc/postfix/sender_canonical
     # cat /etc/stunnel/stunnel.conf
     [smtp-tls-wrapper]
     accept = 12345
@@ -59,11 +64,45 @@ There's also a [blog post by Tim White][TW] which I found useful.
 Because Verizon lacks [STARTTLS][] support, his approach didn't work
 for me out of the box.
 
+Incoming mail
+=============
+
+In case you have trouble with someone blocking your incoming mail, things are a bit trickier.  You can always accept mail on different ports (e.g. the submission port 587), with an entry like
+
+    submission inet n - n - - smtpd
+
+in `/etc/postfix/master.cf`.  However, others will not know which port
+you selected, because [MX records][MX] do not allow you to specify
+alternate ports.  The more modern [SRV record][SRV] allows this, but
+mail systems are old-school and don't support SRV.  If you have access
+to another external server (whose port 25 isn't blocked), you can
+point your MX record at that server, and have it forward mail to you
+on your strange port.
+
+For the purpose of this example, the remote host has a public IP of
+`1.2.3.4`, and your local site is `example.com`, recieving mail on
+port 587.  All of the following config files are on the remote host.
+
+    # cat /etc/postfix/main.cf
+    …
+    proxy_interfaces = 1.2.3.4
+    relay_domains = example.com
+    relay_transport = relay:[example.com]:587
+    …
+
+For futher details (e.g. if you are relaying to more than one target),
+see the [Postfix suggestions for being an MX host for a remote
+site][host].
+
 [Postfix]: http://www.postfix.org/
 [postconf]: http://www.postfix.org/postconf.5.html
 [SASL_README]: http://www.postfix.org/SASL_README.html
 [TW]: http://www.zulius.com/how-to/set-up-postfix-with-a-remote-smtp-relay-host/
 [STARTTLS]: http://en.wikipedia.org/wiki/STARTTLS
+[MX]: http://en.wikipedia.org/wiki/MX_record
+[SRV]: http://en.wikipedia.org/wiki/SRV_record
+[relay_domains]: http://www.postfix.org/postconf.5.html#relay_domains
+[host]: http://www.postfix.org/STANDARD_CONFIGURATION_README.html#backup
 
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