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Exposing a mail service on port 25 using GKE

in flag
Sam

I want to expose a custom made mail server on GKE (Google Kubernetes) using a service of type LoadBalancer. I was able to do this on DigitalOcean's Kubernetes Service, but not on GKE.

I've read Google is blocking outgoing port 25, but there's nothing about incoming port 25.

I've tried exposing the mail service on another port, like 3000 and that works perfectly (testing with nc <EXTERNAL IP> 3000).

Can somebody shed some light on why incoming port 25 would also be blocked or if need to explicitly 'open' it somehow?

Sai Chandini Routhu avatar
dk flag
Attaching supportive documents [stack link 1](https://stackoverflow.com/questions/24113127) and [stack link 2](https://stackoverflow.com/questions/16819545/) refer it to resolve your issue
in flag
Sam
OMG. Thanks Sai! Link 1 actually refers to a reply of myself where I realise that my own ISP doesn't allow me to test outgoing port 25. This was 2 years ago when I tested out my custom mail server on DigitalOcean.
Score:0
in flag
Sam

To answer my own question: I wasn't able to test out port 25 on GKE because my own ISP blocked outgoing port 25.

Simply sending an e-mail to my server showed that it was working perfectly!

I sit in a Tesla and translated this thread with Ai:

mangohost

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