Is there a rate limit for port25check.cloudron.io?

[luckow]

Today is “Frühjahrsputz” and I am connecting a lot of new domains to one of our Cloudron instances. Currently, there are at least 35 domains that should receive mails. After activating (let's say) 10, the web frontend is slow and every status icon is glowing red. The SMTP status says: `Connection to port25check.cloudron.io aborted. Check if port 25 (outgoing) is blocked". I wait 5 minutes and everything is green again.

[nebulon]

I don't believe so. You can run the same test with telnet port25check.cloudron.io 25 Does that work?
Overall it might be slow with many domains, as the calls are partly in sequence. It shouldn't fail (red indicator) though.

Do you have any outbound firewall or so on that server? Some VPS provider might rate-limit that port, but mostly they block that altogether.

[luckow]

adding domains twice and activating the inbox. Instead of 5 minutes, it took up to 30 minutes to switch back to green. No rate limit or firewall on the provider side. Best guess: it's slow with many domains. Let's see.