Mail v6, how

[Ninho]

Assume I will run an MX on IPv6 at home; it can't listen on TCP v4 too, for my friendly ISP has blocked incoming port 25 for awhile.

So I would point an MX record for one of my "Google Apps" domains to my home machine. May I expect most foreign SMTP servers will indeed contact me using TCPIPv6 ? Or will I be losing mail ? I assume Google Apps own MX (aspmx.l.google.com, etc.) must have both A and AAAA records in the DNS. I would define Google's as secondary MX, and expect thrid party MX to fail over to Google's IPv4 servers if they can't do v6.

Does this look correct, please ?

posted to the wrong section I'm afraid, too late to change :(

[broquea]

Probably easier, is that your ISP block port 25 on ipv4 only. If you have a tunnel with us, try the new NMAP feature in the broker's webUI and have it scan an IP allocated to your tunnel, you are trying to bind an MTA to.

[Ninho]

Probably easier, is that your ISP block port 25 on ipv4 only. If you have a tunnel with us, try the new NMAP feature in the broker's webUI and have it scan an IP allocated to your tunnel, you are trying to bind an MTA to.

No need for a scan, my ISP blocks only on IPv4 (couldn't be otherwise, they don't do IPv6 "native"... else I wouldn't be here in the 1st place!).

Is my question unclear ? I'm concerned whether in practice having an IPv6 only mail server at home will work. I'm thinking of adding a solid secondary MX such as those Google Apps provides for free use, will this solve the problem of foreign servers being not v6 enabled (if there indeed is a problem) ?

[jimb]

My guess is that you are talking about doing something like this:

Code Select Expand

$ORIGIN mydomain.tld
  IN MX 5 ipv6mx.mydomain.tld.
  IN MX 10 ipv4mx.someotherdomain.tld.  ;backup IPv4 MX that can do SMTP over port 25

ipv6mx  IN AAAA 2001:DB8::123


I think this scenario will work.  It should work like this:

• IPv6 capable mail servers will deliver directly to the higher priority MX (ipv6 one).
• IPv4 only mail servers will fail to find an A record associated with the IPv6 MX, and move to the next lower priority MX record.

It works when I tested it on a IPv4 only sendmail box with just such a config.  I had the IPv6 set as the higher prio MX, and the IPv4 set as lower.  It skipped the IPv6 MX and moved right on to the IPv4.

You could always give it a try on a test (sub)domain to see how it works with a variety of mail servers on the internet.  :P

EDIT: I also tested it by sending mail from gmail to the test domain set up in this fashion, and it worked (delivered it via IPv4 to the backup MX ... apparently gmail SMTP servers don't do IPv6 yet).

[Ninho]

My guess is that you are talking about doing something like this:

Yep!

I think this scenario will work.  It should work like this:

• IPv6 capable mail servers will deliver directly to the higher priority MX (ipv6 one).
• IPv4 only mail servers will fail to find an A record associated with the IPv6 MX, and move to the next lower priority MX record.

It works when I tested it on a IPv4 only sendmail box with just such a config.  I had the IPv6 set as the higher prio MX, and the IPv4 set as lower.  It skipped the IPv6 MX and moved right on to the IPv4.

You could always give it a try on a test (sub)domain to see how it works with a variety of mail servers on the internet.  :P

EDIT: I also tested it by sending mail from gmail to the test domain set up in this fashion, and it worked (delivered it via IPv4 to the backup MX ... apparently gmail SMTP servers don't do IPv6 yet).

Thanks, Jim.