SMTP timeout failure about listmonk HOT 9 OPEN

I should add that I use the exact same SMTP server, with the exact same SMTP settings, on the same server, in an app in a different container, and that works without failing after a period of time.

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hm, this seems related to #1837 and similar issues in the past. The app's attempt to establish an outgoing TCP connection fails. This has to be in Docker/network/environment/firewall ... At his point, I'm at a loss ;(

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I don't know if this helps, but if I setup the smtp with the correct settings, the test email goes through.

Next, I click save settings, app reloads, I am still able to successfully send the test email (without leaving the page).

However, if I leave the page (go to dashboard for example) and return to the smtp settings, the test email fails with the i/o timeout error.

If I then change a setting like TLS from STARTTLS to TLS/SSL, and back to STARTTLS (never clicking save or anything else) the test email goes through just fine. There appears to be a bug in here, but I don't know go/js enough to start digging.

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When you change any setting and save, listmonk does a full restart. So something's getting flushed/cleared which is why it works. Then whatever's blocking the connection kicks in and connections fail. I'm at a loss here as to what could be blocking the connections and how.

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I think you misread what I said. When I change a setting BUT DON'T SAVE, it also works.

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That's just a coincidence. Changing the setting on the UI without hitting save has no effect on the backend. That's just a browser/UI thing.

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I tried to create a screen recording to show, and its true I can't get it to reliably reproduce the timeout error every time.

I will try running listmonk as a standalone binary and see if the error still exists.

Thank you anyways for the great app!

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If you're using docker it may be a firewall issue. See #1837 (comment).

Docker may be opening some ports after you make a change, and then your firewall blocks them again.

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@MaximilianKohler Thanks for the feedback, but firewalld with podman does not have the same outgoing restrictions. As stated above, the issue is intermittent. I will also try increasing the number of retries, and the timeout/wait times to see if it will clear up the issue.

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