I have a non-gmail account with a cache of messages in my android gmail app. How can I make a backup of the emails and attachments? Accessing the mail server to make a backup is not possible. I tried the method in the answer here: Backup gmail emails offline However, the backup file is too small to realistically contain the emails and attachments. It's only coming out 549 bytes, even with trying a few different adb backup options.
android:allowBackup="true"
therefore app backup via adb should be possible. Try to backup a different app to test ifadb backup
works at all on your device. – Robert Apr 9 '20 at 14:30