Apple Mail – IMAP – Stucking “Copying Messages”

Issue: Apple Mail activity window stuck on “Copying Message” for IMAP account.

Resolution: Hidden folder “OfflineCache” must be deleted.

To show hidden files: Open terminal and enter the command:

defaults write com.apple.Finder AppleShowAllFiles YES

To delete the offending folder:

Close Apple Mail app,
Go to “/Users/[Your user]/Library/Mail/
Find the folder titled “IMAP-[ACCOUNT]” where [ACCOUNT]” is the name of the e-mail account you’re having trouble with,
Delete the folder “OfflineCache”,
Open Mail app, Activity window will be more active.

Would be advisable to hide the hidden folders again:

defaults write com.apple.Finder AppleShowAllFiles YES

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