How to prefer ipv4 binding when sending email ?

[dtrckd]

I am experiencing spam blacklisting issues from some domains due to ipv6 range allocation and would want to send email with the ipv4 address instead of ipv6.

Is there a way to ask Postal to prefer ipv4 address binding when sending mail ?

Note: Just to mention, there is a smtp_address_preference setting in Postfix to address that.

[willpower232]

if the receiving email server has IPv6 available then Postal will always default to using that if its bound to :: so has access to your IPv6 addresses

You could try binding to 0.0.0.0 instead which should stop you using IPv6 altogether but if you're having spam issues then it might not just be down to your IP address.

[willpower232]

Interesting, I guess with such a vast quantity of addresses available, they're presuming people are allocated specific blocks rather than individual ones maybe? Unfortunate but I guess it depends what support you can get from your server/internet company.

[dtrckd]

Yes, I think it's like that too.

I am just getting back that to this point, but I am really curious about it :

1. do you think that implementing a feature supporting smtp_address_preference = ipv4||ipv6 ", which will try to send email binding to one address/interface first will be that hard ?
2. if it is proposed as a contribution, does the postal team will be interested to merge it eventually ?

[willpower232]

It doesn't sound impossible but its way out of what I know about how to bind to ports. If you or someone makes a PR at least then the code will exist and people that need it can make their own docker image if it doesn't get merged.

[dtrckd]

I resume this discussion because I am still curious why this issue does is not get more attention (Are people using Postal more for internal emailing than marketig ?) ;
More specifically, when getting a softfail with an error message from the remote server that suggest that the email was rejected because of the sender IP in a spam list, one could try to send with the other IP addresses (if they are multiples addresses, but basically IPv4 and ipv6 cohabitation seems to be ubiquitous.) which could solve the error if the other address is not listed...

[dtrckd]

Some interesting point to consider already mentioned here #605

[vulnfind]

where can I find the setting of smtp_address_preference ???? is it in postal.yml and if yes under which heading i have to put it under??? smtp: or smtp_server: ???

[stef157]

Hi, is there some ETA about this smtp_address_preference ?