Gmail and smtp over IPv6 FYI



  • FYI - google won't accept email via smtp over IPv6 if you don't have a reverse DNS v6 record for your mailserver's v6 address.

    Having a valid SPF record with IPv6 included isn't sufficient.


  • Rebel Alliance Global Moderator

    Do they accept email from ipv4 if you don't have a reverse?  I don't believe many major players well accept mail from your mail server if you don't have a ptr, and quite often it better match your forward (FCrDNS)

    ie if your mail server reports its name as smtp.domainX.tld then your PTR better report smtp.domainX.tld as well when they check the IP you connected to them from.

    So are you saying gmail accepts mail from your mail server if you don't have a ptr on your IPv4?



  • @johnpoz:

    So are you saying gmail accepts mail from your mail server if you don't have a ptr on your IPv4?

    Good point - I suspect a lack of some kind of reverse lookup would contribute to the "badness" of the connection.

    My point is that my ISP doesn't have a reverse nameserver assigned for my block (prefix)  so its a potential gotcha.

    I managed to work around it by updating my SPF record to specifically include a v6 address.


  • Rebel Alliance Global Moderator

    SPF is not the same as a PTR, and how would that solve your problem when you just stated that gmail doesn't accept email from servers that don't have PTR.

    "FYI - google won't accept email via smtp over IPv6 if you don't have a reverse DNS v6 record for your mailserver's v6 address."

    You stated that spf is not sufficient - now your saying it is?

    "Having a valid SPF record with IPv6 included isn't sufficient."
    "I managed to work around it by updating my SPF record to specifically include a v6 address."

    If your isp supplies you with a /64 then they should provide the the ability to update your own ptr.  Hurricane electric allows for this with the /48 or /64s they give you for free.

    Who is your isp?