Configuring a smtp_relays does not honor the routing table.

[cvillabrille]

Describe the bug

Configure a smtp_relays server in postal.yml, and some domains in the routing section.

Sending and email with multiple recipients, if the first email in To is external (not included in the routing), Postal does not honor the routing table and forward the delivery of the email of all recipients to the relay_host, and does not attempt to deliver the domains configured in the routing section.

A clear and concise description of what the bug is.

Configuring:

• smtp_relays with a valid relay server (relay.somedomain.com)
• domain1.com routing to smtp.domain1.com
• domain2.com, routing to smtp.domain2.com

One email sent to :
[email protected]; [email protected]; [email protected].
Postal will honor the routing and forward the email to domain1.com, domain2.com and gmail.

However, if the first emails in To: is an external email (to be forwarded to the relay, i.e. gmail), all the delivery is forwarded to the relay server, including those (domain1 and domain2) configured as routing. Postal does not try to delivery domain1.com and domain2.com by itself.

To Reproduce

1. Configure the smtp_relays value in postal.yml.
2. Add a routing to domain1.com with a valid smtp server.
3. Prepare an email to: [email protected] ; [email protected]
4. Email to [email protected] is not delivered by Postal but sent to the smtp_relays server since the first email in the list is external.
5. While if you set first [email protected] ; [email protected], the email to domain1.com is delivered by postal and the one to Gmail is forwarded to the relay_host.

Expected behaviour

Honor the routing does not matter which is the first email in To:

A clear and concise description of what you expected to happen.

Does not matter which email address is set the first. Postal must check if the email is to be sent to the relay server and for those configured in the routing section, try to deliver the email to those domains.

Environment details

• OS: Ubuntu 24
• Postal version: latest

[willpower232]

I don't think smtp_relays does anything other than send all email from Postal via a specific channel, I don't think it has the logic you're thinking of in it.

[cvillabrille]

Hi Will,

thanks for the reply.

That's the weird thing here. The point is, if I change the order and the domain1.com or domain2.com (that I have a routing definition) are the first email in the To: list, Postal has that logic and attempt to delivery to domain1.com, domain2.com and the rest addresses to the relay_host.

Only if I start the To: list an email considered as "relay" then is when it does not attempt to delivery domain1.com and domain2.com, just forward and let all the responsibility to the relay_host.

Weird, isn't?