I finally got around to trying the copy and replace of the Thunderbird folder.

Unfortunately, it didn't work although there was a little progress. During my latest attempt at encrypting my Thunderbird folder, the encryption process did actually start before stopping suddenly midway.
Here are my Console logs:
12/10/14 12:11:46.441 AM Espionage[461]: WARN (-[TEAppDelegate isGoodFolderAtURL:error:]:1183): Only encrypt folders in the Library folder if you know what you're doing. If you're encrypting application data, do not run the application until its data is unlocked. Are you sure you want to do this?
12/10/14 12:12:49.384 AM Espionage[461]: ERROR (-[NSFileManager(TEAdditions) copyOrMoveContentsFrom:intoLocationAt:destinationName:options:upOneLevel:cancelBlock:move:error:]:490): failed because: !subitems
12/10/14 12:12:49.384 AM Espionage[461]: ERROR (-[NSFileManager(TEAdditions) copyOrMoveContentsFrom:intoLocationAt:destinationName:options:upOneLevel:cancelBlock:move:error:]:509): error 260 durng copy of: file:///Users/deer/Library/Thunderbird/
12/10/14 12:12:49.386 AM Espionage[461]: ERROR (+[DiskMaster createDiskForFolderFace:diskInfoSettings:options:icon:error:]:264): failed copy of /Users/deer/Library/Thunderbird into diskimage file:///Users/deer/Library/Application%20Support/com.taoeffect.Espionage3/Data/Temp/82DA9DCD-E72E-4F2C-8D37-96BE7CF0C054.sparsebundle
12/10/14 12:12:50.644 AM Espionage[461]: ERROR (-[EncryptFolderTask go:]:140): Error creating disk image for 'Thunderbird': Error Domain=Espionage Code=260 "Error during copy: The file “Thunderbird” couldn’t be opened because there is no such file.
Could not copy all of: /Users/deer/Library/Thunderbird
See system log for more." UserInfo=0x600000667ec0 {NSLocalizedDescription=Error during copy: The file “Thunderbird” couldn’t be opened because there is no such file.
Could not copy all of: /Users/deer/Library/Thunderbird
See system log for more.}
12/10/14 12:12:50.646 AM Espionage[461]: WARN (-[EncryptFolderTask go:]:238): Error during copy: The file “Thunderbird” couldn’t be opened because there is no such file.
Could not copy all of: /Users/deer/Library/Thunderbird
See system log for more.
12/10/14 12:13:03.453 AM Espionage[461]: INFO: backed up: /Users/deer/Library/Application Support/com.taoeffect.Espionage3/Backups/database3 2014-12-10 001303
Any new ideas? Thanks!