POSIX 54 Error in Mail (iCloud Custom Domain)

Rackspace is aware of the issue. This screenshot is from my Rackspace admin account. Their suggested workaround, i.e., using Webmail, doesn't really help because their Webmail is not set up to be responsive to small screens, so its pretty much unusable.

I bought a new iPad with 18.0.1 a few weeks back, and I just got the POSIX 54 error for the first time today. But I am connecting to my gmail email account, not iCloud or any of the other mail servers also discussed in this thread.

I can still access my gmail via my desktop, Samsung phone, and even on the iPad by using Safari to log into the gmail account. But not working with email account defined on the iPad.

The POSIX 54 error in Mail when using iCloud Custom Domain appears to be a recurring issue since the 18.0.1 update. After troubleshooting, I've found a solution that resolves the error, restoring full functionality to the Mail app with the iCloud Custom Domain. If you're facing this issue,

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Yes having ‘upgraded’ from 12 pro max to a 16 pro max I have been plagued by POSIX 54 mail errors. My wife upgraded from 12 pro to a 16 pro max and she is also having the same issues. I’m told it’s a known Apple Mail issue but still no fix…..

It seems to happen to all of us in different scenarios. For me it's getting gmail on iPhone and if I'm on cell. I have to go onto wifi. I have to call Apple support this week to get some options. I can't pick up any mail once I'm out.

Well spotted, yes I use RackSpace Email. The issue is intermittent, annoying and I hope fixed soon!

Never mind - I just got the error over 5G as well. :(

Having the same issue with iPad OS 18.1

Definitely not happy about this, I hope that Apple fixes this problem soon.

Glad it worked for you. I don't use iCloud mail, so that isn't the definitive solution.

I’ve deleted all email accounts and then added them again without solving the issue sadly.

I’m not using a VPN, but thanks for your suggestion.

Tried it with and without VPN. Same either way.

If it recurs, please post back here.

Unfortunately the issue has returned.

That worked for my, thanks!