Metronet - Intermittent "exceeded maximum cached connections" issue

[#1]

Apologies if this has been raised before,  can't find it.  Intermittently (but frequently, 3 or 4 times a day) - I'm getting a "could not connect" message,  telling me that I've exceed the the maximum number of cached connections to the server,  and suggesting I reduce them in settings (Thunderbird).  So I've reduced the maximum - right down to one,  to no effect.  Happens completely at random on any device I use,  Thunderbird or otherwise, including iPhone (on the latter,  I just get a helpful "there was an error" message).  The problem goes away of its own accord after half an hour or so.   I'm not a techie - something getting stuck at the PN end? 

Presumably just part of the increasing flakiness of metronet - i really should move on but it would be right a bummer as I was one of the original MN signups, back in God-knows-when,  and the thought of decades-worth of unravelling just makes my head hurt. 

[#2]

Hiya @pwberry, thanks for getting in touch.

I'm sorry that you're having some issues with your emails and for the frustration this causes!

When did the issue start? Do you have a large amount of emails in the inbox? If you log in via webmail, do you get similar errors?

[#3]

Interesting - a scenario I have never encountered ... but I have neve used Thunderbird.

I often find that Googling the full text of an error message delivers helpful guidance and sometimes fixes - see for example Unable to connect to IMAP - Exceeded Maximum Number of Connections | Thunderbird Support Forum | Moz...

Interesting also that all of the hits searching for "exceed the the maximum number of cached connections to the server" exclusively mention Thunderbird's email client ... might the answer be to switch to a better email client?

[#4]

Thanks for reply @LaurenB ,  It's been an issue ever since The Great Outage of Nov '21,  didn't bring it up earlier as I was just so relieved to get my email service back 🙂    Webmail is fine, no issues,  There are some suggestions pointed to by @Townman that I'll check through first. 

kind regards

Paul

[#5]

Thanks for reply @Townman, and suggestions.  I'd be inclined to suspect Thunderbird however I run a couple of work email accounts via T'bird and it's only the Plusnet / metronet one where I get this issue.  The other accounts work fine with the max number of cached connections set to 5.  Nevertheless I'll try a different email client to see if I get the same problem.
Also In the discussion you point to there's also mention of iPhones being susceptible to hogging connections so I'll check that one out as well. 
kind regards
Paul