I’m wondering if just switching the MX record on my domain to point to the new email server is somehow messing up my IMAP connection to my older server.
Changing your MX record shouldn’t normally cause any issues as it just points your Incoming mail to your new server account mailbox and so it only just affects new mail arriving in that time.
So if you have been dragging / moving email from your old IMAP account to your new IMAP account on a new mail server and it’s not all appearing after moving it, that just means eM Client is still synching / uploading the email to your new server which can take time to appear on the new server depending on your upload speed and how much mail is in each folder etc.
However as you are now getting errors downloading or uploading with your desktop and laptop if nothing is synching in Show Operations, and is a constant error, then it’s either a server mailbox error on your old or new server, or it’s a local database error. You probably will need offical support to determine that and what to do.
So, it looks like the Trash has record of a folder I can’t see. I looked at the “properties” of the trash folder and clicked on Repair but it didn’t seem to do anything or help; neither did closing and re-opening eM Client
You could normally manually run the local database repair to fix the trash folder in eM Client as per @gary links for PC and Mac , but the problem with doing that is because you are in the middle of moving emails from one server mailbox to another server mailbox “that would clear your local cache of any current emails uploading / transferring” from your old IMAP account to your new IMAP account so that’s not an option you can do in this case.
So id suggest if you have a current active paid Pro, Personal or Business account go to the VIP support page and login and lodge a support ticket and link this thread so they can see what you have done so far and include your logs in ticket.
If you have run out of your offical 12 months support you can get another year support via the following page. VIP Support Extension | eM Client