I will take your word for the IONOS folk not limiting concurrent IMAP connections, but they would be very unusual in that decision.

Perhaps log the imap connection and see what it is all about. https://wiki.mozilla.org/MailNews:Logging

But before I did that, I would be looking at the error console (ctrl_Shift+J. This is a rather messy place as every error or warning is logged for all actions and a lot of it is really irrelevant. So the first thing to do is clear the console using the trash button on it's toolbar.

Now try and download the mail from the imap account. What do you get logged in the console? Other than what you already know. It is reporting a possible lack of available connections.

It may be an issue with third party software like an antivirus that has it's own limit on connections it can scan. Perhaps try without any email scanning.

Hi Matt, Thanks for that.

I don't see any details in the logging console at all when I receive emails. I've tried this on a PC which is giving the error and also one that's working ok.

Reading the https://wiki.mozilla.org/MailNews:Logging is shows that IMAP logging isn't available on version 115 :-(

imap (not available in version 115) - mailnews.imap.loglevel string, set to All, but only if you have set mailnews.imap.jsmodule=true for Beta and Daily channel builds only.

I disabled the firewall too and it was the same.

Any other thoughts?

Cheers

Phil

I've attempted to enable a gecko log file using these command line instructions that I found on another thread.

export MOZ_LOG="IMAP:5,timestamp" export MOZ_LOG_FILE="/home/philc/logs/imap.log"

I created this directory just in case.

I restarted TB but no file.

How am I being stupid is a question I ask of myself frequently so please don't assume that I have carried out some required task before this will work.

Thanks

In all cases that I've ever come across that message means there are limits on concurrent connections to server when using imap.

Those connections mean all connections to server accumulated from all computers, phones etc. The normal method of a fix is to set the cached connections in Thunderbird to 1. Then exit Thunderbird. Repeat on each computer. Do not restart any Thunderbird until all computers have been set to cache connection = 1 and closed down. Sometimes it can take a few minutes for server to recognise connection has closed.

I did find out that ionos do have limits on ftp https://www.ionos.co.uk/help/hosting/setting-up-and-managing-ftp-access/ftp-error-messages-explained/

Are you using ionos with a google workspace or microsoft exchange package?