Keeping a mailbox offline


I’m using Em Client, and I stopped using one of my email accounts, therefore not renewing the domain.  Eveytime I open Em Client it tries and fails to connect to it, which is normal. 
However, how could I set up this account to be “offline” or something ? I just want to keep an archive of it’s emails and don’t want to delete the archived emails, but the failing connection popup is a bit annoying.

Thanks in advance for your replies !

Move the messages to Local Folders, then remove the old account from eM Client. If Local Folders are not visible, you can enable them in Menu > Tools > Settings > General > Show Local Folders.

Thank you Gary !