SMTP timeout after updating to 8.3.1

[rupertsworld]

I recently upgraded my Cloudron and have been running into an apparent bug with the SMTP relay.

Without changing any settings, suddenly the connection to my Postmark SMTP relay times out, and won't connect. I tried with a Fastmail SMTP server and this has the same issue.

The only things that have changed:

• I upgraded the size of the instance on Digital Ocean
• I upgraded to the latest version of Cloudron

Any idea what could be causing this? I can’t schedule meetings or receive notifications, and my Cloudron runs my company of 6 people currently, so this is critical.

[robi]

check to see if you're using IPv6.

[rupertsworld]

Is that something I should or should not turn on?

I tried configuring but got the following error:

[robi]

Check the other threads on the forum about ipv6 issues, it's best to disable it on the entire OS until a solution is found.

[joseph]

@rupertsworld can you try curl -6 https://ipv6.api.cloudron.io/api/v1/helper/public_ip on the server ? Looks like that fails. Next step is to see if host ipv6.api.cloudron.io works or not.

[rupertsworld]

For the first command (curl):

curl: (7) Failed to connect to ipv6.api.cloudron.io port 443 after 1055 ms: Couldn't connect to server

For the second command (host):

ipv6.api.cloudron.io has IPv6 address 2604:a880:800:10::b66:f001

@joseph

[joseph]

@rupertsworld so DNS resolution is working. You can try ping6 2604:a880:800:10::b66:f001 . It looks like there is some IPv6 networking issue in your server. Maybe you can disable IPv6 altogether and also in Cloudron Network -> IPv6 disable it (then Sync DNS as well to remove the AAAA DNS entries).

[rupertsworld]

I disabled IPv6 & synced everything, but still cannot connect to an SMTP server (having major problems sending people calendar invites at the moment)

[joseph]

@rupertsworld you have to disable IPv6 on the server (and not just in Cloudron UI). The Cloudron UI only does not set up AAAA records, does not remove IPv6 on the server as such .

[rupertsworld]

OK so I need to go through some steps to disable IPv6 on the command line of my Droplet.

But I'm confused – I only enabled IPv6 in response to the first comment here, which I interpreted as suggesting I enable it. So, is IPv6 responsible for the SMTP server connection failures?

[rupertsworld]

I've disabled IPv6 on the server and am still getting connection timeout issues for any SMTP server.

[rupertsworld]

I've now also tried with Mailgun following their setup instructions and get the same timeout error

[rupertsworld]

There are also some AAAA records I cannot delete

[nebulon]

The initial error was the outbound ipv6 connection which failed, so you have to disable ipv6 on the server itself. This has little to do with the AAAA record, as that would be for incomming connections!
You may have to contact your server provider on how to disable ipv6 (network wise) on the server. Just to get ipv6 issues out of the way first. Ipv4 is totally sufficient anyways for the moment, so best to get those potential issues out of the way.

[joseph]

@rupertsworld where is this screenshot from?

[rupertsworld]

Apologies for the lack of context – this is through the Digital Ocean app integration with Cloudron

[joseph]

@rupertsworld Interesting... Cloudron only has a marketplace image on Digital Ocean . AFAIK, we don't have any app integration . It could be that DO implemented some features on their side without our knowledge .

[joseph]

This is/was an issue with DO blocking outbound 587.

See also https://docs.digitalocean.com/support/why-is-smtp-blocked/ . Bit ironic they want to use all these sketchy SaaS email providers. They keep changing ownership to various marketing companies. I thought DO being an infra company will know better..

[rupertsworld]

Yeah can confirm, and thanks for the help diagnosing. I wasn't given any advanced notice of the SMTP block, it was hidden in release notes somewhere. This is now unblocked.