See e.g. @ jdaviescoates said in Cloudron 8.2 Released : @ jdaviescoates said in Cloudron 8.2 Released : Warning to everyone on 8.2: it seems lots of things (including email delivery) break now break if you don't have lots of ipv6 stuff set-up already on your server, e.g. I just got this: "message": "Upstream error: 450 4.7.25 Service unavailable, sending IPv6 address [2a01:4f9:6b:54cd::2] must have reverse DNS record (S820). [ LO1PEPF000028CD.GBRP265.PROD.OUTLOOK.COM 2025-01-14T11:30:53.543Z 08DD32A234230673]" I'm unclear why such crucial things were allowed to break with this update - I don't recall seeing any warnings on here about setting up ipv6 stuff before updating (and perhaps auto-updates shouldn't've have happened at all without such warnings being read). It seems to me that the email status check stuff needs to be updated - given the warning above I evidently should not be getting a green light for my PTR I read somewhere that one way to avoid issues with IPv6 stuff was to just have it completely disabled. But I found the settings in Network: In my case it was already disabled, and so that obviously wasn't helping. I found: @ girish said in IPv6 issue : Also, If you use programmatic DNS, then you can just go to Domains -> Sync DNS (after enabling IPv6). It will setup the DNS entries automatically. So I've done this: in Network: under IPv6 section I chose Public IP in Domains -> hit Sync DNS Now I guess I just need to work out how to set-up IPv6 PTR/rDNS/reverse DNS on my Hetzner server - then perhaps I'll be able to send emails again!

To summarize the situation: starting 8.2, it seems the mail server has started to prefer using IPv6 for gmail. This wasn't a change in Cloudron consciously at least. I have looked into the Haraka changes and cannot find anything specific there either. I do see that gmail has IPv6 mail servers now, not sure if they were there before or not. To fix the situation, you simply have to set IPv6 PTR record . Cloudron has not implemented a IPv6 PTR check in 8.2 but a check is implemented for next release. The PTR record is set in the VPS provider. Usually, IPv6 is allocated a block of addresses and not a single address like IPv4. If you run curl https://ipv6.api.cloudron.io/api/v1/helper/public_ip , this will give you the specific IPv6 address that Cloudron is using to connect to gmail. You have to set the PTR for this specific IPv6 address. If your VPS provider does not allow you to set IPv6 PTR , then just disable IPv6 in the interfaces. sysctl -w net.ipv6.conf.ens18.disable_ipv6=1 for example . You have to put net.ipv6.conf.ens18.disable_ipv6=1 in your /etc/sysctl.conf for this to persist reboots. After you do this, also disable IPv6 in Cloudron, Network -> IPv6 -> Disable.

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Email sending broken after updating to 8.2.x (due to IPv6 issues)

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Email sending broken after updating to 8.2.x (due to IPv6 issues)