I have a large email that will not not send. I need to clear my sending box and then delete them. I will need to remove them from trash also.
If I have understood right you can’t even delete this email completely?
Anyway send me please your SMTP and IMAP logs, Tools - Settings - Advanced, mark off IMAP and SMTP, apply and restart eM Client
then simulate steps which leads to your issue and send logs… to email@example.com together with this topic’s URL or at least it’s subject.
after you can turn logging off.