Smtp_address_preference - Does anyone know where this is

shoulders · October 30, 2024, 12:52pm

SYSTEM INFORMATION
OS type and version	Ubuntu Linux 22.04.5
Usermin version	2.102
Virtualmin version	7.20.2 Pro
Theme version	21.20.7
Apache version	2.4.52
Package updates	10 package updates are available

https://www.postfix.org/postconf.5.html#smtp_address_preference

I am trying to find this option in the webmin GUI, it might not exist but does anyone know where it is?

I need to set it to IPv4 rather than the default option of IPv6 as my server does not have IPv6.

for those looking it should fix mail errors in postfix such as:

Host or domain name not found. Name service error for name=example.co.uk.mail.protection.outlook.com type=AAAA: Host not found, try again

Thanks

forlotto · October 31, 2024, 5:07am

From the website so people don’t have to follow a link.

**smtp_address_preference (default: any)**

The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP client will try first, when a destination has IPv6 and IPv4 addresses with equal MX preference. This feature has no effect unless the [inet_protocols](https://www.postfix.org/postconf.5.html#inet_protocols) setting enables both IPv4 and IPv6.

Postfix SMTP client address preference has evolved. With Postfix 2.8 the default is "ipv6"; earlier implementations are hard-coded to prefer IPv6 over IPv4.

Notes for mail delivery between sites that have both IPv4 and IPv6 connectivity:

* The setting "[smtp_address_preference](https://www.postfix.org/postconf.5.html#smtp_address_preference) = ipv6" is unsafe. All deliveries will suffer delays during an IPv6 outage, even while the destination is still reachable over IPv4. Mail may be stuck in the queue with Postfix versions < 3.3 that do not implement "[smtp_balance_inet_protocols](https://www.postfix.org/postconf.5.html#smtp_balance_inet_protocols)". For similar reasons, the setting "[smtp_address_preference](https://www.postfix.org/postconf.5.html#smtp_address_preference) = ipv4" is also unsafe.
* The setting "[smtp_address_preference](https://www.postfix.org/postconf.5.html#smtp_address_preference) = any" is safe. With this, and "[smtp_balance_inet_protocols](https://www.postfix.org/postconf.5.html#smtp_balance_inet_protocols) = yes" (the default), only half of deliveries will suffer delays if there is an outage that affects IPv6 or IPv4, as long as it does not affect both.
* The setting "[smtp_address_preference](https://www.postfix.org/postconf.5.html#smtp_address_preference) = ipv4" is not a solution for remote servers that flag email received over IPv6 as more 'spammy' (the client IPv6 address has a bad or missing PTR or AAAA record, bad network neighbors, etc.). Instead, configure Postfix to receive mail over both IPv4 and IPv6, and to deliver mail over only IPv4.
> /etc/postfix/[main.cf](https://www.postfix.org/postconf.5.html): [inet_protocols](https://www.postfix.org/postconf.5.html#inet_protocols) = all

> /etc/postfix/[master.cf](https://www.postfix.org/master.5.html) smtp ...other fields... smtp -o [inet_protocols](https://www.postfix.org/postconf.5.html#inet_protocols)=ipv4

These all all settings set in post config and main config so it’s just a matter of changing them respectively there I believe.

Currently inet protocols for mine is set to ipv4

shoulders · October 31, 2024, 8:56am

thanks for that, but I knew it was in main.cf I was looking for them in the GUI.

Couldnt find them so did a feature request.

github.com/webmin/webmin

postfix - Add IPv4 and IPv6 protocol handling settings

opened 01:57PM - 30 Oct 24 UTC

shoulders

| SYSTEM INFORMATION || |----------|----------| | OS type and version | Ubun…tu Linux 22.04.5 | | Usermin version | 2.102 | | Virtualmin version | 7.20.2 Pro | | Theme version | 21.20.7 | | Apache version | 2.4.52 | | Package updates | 13 package updates are available | ## The Background By default Postfix accepts and sends emails by IPv6 and IPv4 with a preference for IPv6. The protocol handling seems to be handled by the following settings shown below with their defaults: - **[inet_protocols](https://www.postfix.org/postconf.5.html#inet_protocols) = all** - The Internet protocols Postfix will attempt to use when making or accepting connections. - When both IPv4 and IPv6 support are enabled, the Postfix SMTP client will choose the protocol as specified with the [smtp_address_preference](https://www.postfix.org/postconf.5.html#smtp_address_preference) parameter. Postfix versions before 2.8 attempt to connect via IPv6 before attempting to use IPv4. - **[smtp_address_preference](https://www.postfix.org/postconf.5.html#smtp_address_preference) = any** - The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP client will try first, when a destination has IPv6 and IPv4 addresses with equal MX preference. This feature has no effect unless the [inet_protocols](https://www.postfix.org/postconf.5.html#inet_protocols) setting enables both IPv4 and IPv6. - **[smtp_balance_inet_protocols](https://www.postfix.org/postconf.5.html#smtp_balance_inet_protocols) = yes** - When a remote destination resolves to a combination of IPv4 and IPv6 addresses, ensure that the Postfix SMTP client can try both address types before it runs into the [smtp_mx_address_limit](https://www.postfix.org/postconf.5.html#smtp_mx_address_limit). There are also LMTP equivalent versions of these settings. There might be more related settings ## The issue that caused me to find these settings missing I run my Virtualmin server on an IPv4 only network yet it still tries to use a `AAAA` MX record if it is available. You can see the following errors in the mail queue where the emails are deferred: ![image](https://github.com/user-attachments/assets/480f4561-b2ec-4a96-adf6-413cbd8136a6) > Host or domain name not found. Name service error for name=example-co-uk.mail.protection.outlook.com type=AAAA: Host not found, try again After research the settings mentioned in `the background` need to be modified to remove IPv6 lookups. > this is not a support request for this as I will solve this myself via the `main.cf` by disabling the IPv6 protocol where needed. ## Feature Request These settings can be set via the `main.cf` config file but because of their importance in configuring what protocols that Postfix works on they should have their settings in the GUI so a user can enable/disable the support of IPv6 and IPv4. In Postfix maybe create a new section call `Protocols` or `Network`. ![image](https://github.com/user-attachments/assets/5ea694be-0b97-4a6f-84b7-51873bde9f61) ## Additional When Virtualmin is installed, maybe there should be an option to select your protocol environment i.e.: - IPv6+ IPv4 - IPv6 - IPv4

forlotto · October 31, 2024, 4:17pm

oh sorry
virtualmin on your console
DNS OPTIONS
Allow Sender IPV6 Addresses you can delete the IPV6 address. Only place I know of maybe there is something else.
Hope this helps. It should be what SPF does and is for. Sender Permitted From

forlotto · November 3, 2024, 12:10am

also disable it under the server address locally

Which is under manage virtual server > Change IP Address

That should disable IPV6.

Both of these things the previous post and this postmust be done for each Server 1 by 1 in Virtualmin.

Would be cool if there were change external IP for all servers button

shoulders · November 3, 2024, 8:27am

@forlotto there is always this

Addresses and Networking → Change IP Addresses

system · November 11, 2024, 8:28am

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