How to force IPv4 connections for specific domains if IPv6 is enabled

birdwes edited this page Aug 5, 2014 · 2 revisions

This scenario arose as a result of the ISP (BTNET 21CN) providing IPv6 and then not being able to provide reverse PTR records for the IPv6 addresses. It turns out that RIPE has not given the ISP SOA on that IPv6 subnet yet:

;; AUTHORITY SECTION:         3600    IN      SOA 1407144119 3600 600 864000 7200

As a consequence, some IPv6 capable recipients reject e.g. the following:

2014-08-04 12:31:56 1XEGUa-0006Kb-N8 ** R=dnslookup T=remote_smtp X=TLSv1.2:AES256-GCM-SHA384:256: SMTP error from remote mail server after RCPT TO:<>: host [2620:109:c006:104::215]: 554 5.7.1 The sending mail server at 2a00:xxxx:xxxx:0:xxx:xxx:xxxx:xxxx does not have a reverse (address-to-name) DNS entry cf


Add a domainlist:

domainlist ipv4_force_domains = \ : \ : \ : \ : \

Router configuration

Add a router:

        driver = dnslookup
        domains = +ipv4_force_domains
        transport = ipv4_smtp
        ignore_target_hosts = <; 0::0/0

Transport configuration

Add a transport:

        driver = smtp
        dkim_domain =
        dkim_selector = x
        dkim_private_key = /usr/exim/dkim.private.key
        dkim_canon = relaxed
        interface = <my.v4.ip.address>
Clone this wiki locally
You can’t perform that action at this time.
You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Reload to refresh your session.
Press h to open a hovercard with more details.