Your recycle bin may have become corrupted. Try “right clicking” on your bin / trash folder and click “Properties” at the bottom. Then click the “Repair Tab” at the top and finally click “Repair”.
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Failing that “if you Windows” try running the mail database repair option manually via the “command line dos window” as per Garys post from the thread below.
Note:- Make sure eM Client is closed before running the below database repair command.
(@Gary post
“Close eM Client and open a Windows Command Prompt. Not a powershell, but a command prompt”.
Paste in this command:
“C:\Program Files (x86)\eM Client\MailClient.exe” /dbrepair
Restart eM Client. Any undeletable messages should be removed
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If that still doesn’t fix it, go online to your email via webmail and see if you can clear trash. If you cannot clear your bin / trash online then contact your mailbox technical support to get that fixed.
However, “if you can delete the trash ok online” in your webmail, then “remove and re-add” your email account in eM Client as the account must have then become corrupted in some way.
So if it’s an IMAP, Exchange, Office 365, iCloud (Non-POP) account, then go to “Menu / Accounts” and remove and re-add your account and all your email will come back and that should fix then issue.
Now if its a POP setup, before removing “Create a folder down in Local Folders” at the bottom left in eM Client called eg: Old Mail and then “Drag / Move” all your current POP messages and folders down under Old Mail. Then once you are certain all your email is in Local Folders, remove and re-add your POP account via “Menu / Accounts”.
Note:- Before doing any of the above, backup eM Client via “Menu / Backup” incase anything goes wrong. You can see when the backup is completed via “Menu / Operations”.