White, Daniel E. (GSFC-770.0)[AEGIS]:
> Many thanks for the sanity check, Mr. Postfix
>
> I am using the explicit domain name rather than $mydomain mainly on client
> machines because they are not guaranteed to have the same domain as the mail
> servers.
>
> Is there any way to shorten/remove the delay I saw in the MX-failover ?
By reducing smtp_connect_timeout from the default 300s to a more
reasonable value, maybe 10-30s.
Note that Postfix will shuffle the order of equal-preference MX
hosts, so that a down server will delay only some of the traffic.
Wietse
> Again, many thanks for the quick response
>
> From: <owner-postfix-us...@postfix.org> on behalf of Wietse Venema
> <wie...@porcupine.org>
> Reply-To: Postfix users <postfix-users@postfix.org>
> Date: Wednesday, October 26, 2022 at 14:09
> To: Postfix users <postfix-users@postfix.org>
> Subject: [EXTERNAL] Re: MX records and relayhost: Am I going this correctly ?
>
> White, Daniel E. (GSFC-770.0)[AEGIS]:
> MX Records:
>
> mydomain.tld. 33 IN MX 10
> relay-1.mydomain.tld.
> mydomain.tld. 33 IN MX 20
> relay-2.mydomain.tld.
>
> with relay-1 and relay-2 having appropriate A and PTR records.
>
> Then in /etc/postfix/main.cf, I have
>
> relayhost = mydomain.tld
>
> I have seen this work with relay-1 unavailable.
>
> This is the obvious (to me) approach when the domain has multiple
> MX hosts. It is also similar to the first relayhost example in the
> stock main.cf file:
>
> relayhost = $mydomain
>
> The outgoing message sat in the queue for a brief time, then went
> out through relay-2.
>
> I found a Red Hat solution
> https://gcc02.safelinks.protection.outlook.com/?url=https%3A%2F%2Faccess.redhat.com%2Fsolutions%2F4025391&data=05%7C01%7Cdaniel.e.white%40nasa.gov%7Cec472cf769824ce55a8e08dab77d47f4%7C7005d45845be48ae8140d43da96dd17b%7C0%7C0%7C638024045956278652%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=WFi3rKroF5DsLvomCS5NcG9%2ByCKQOlC3ITI1KFW4oyU%3D&reserved=0
> that suggests using
>
> relayhost = [relay-1.mydomain.tld]
> smtp_fallback_relay = [relay-2.mydomain.tld]
>
> This also works, but it would be less obvious to me.
>
> Wietse
>
>
