First, even though you delete an email from your Gmail Account, the deleted email will be kept in your in your backup folder. When we backup your emails, we only download emails. We do not delete any emails from your local copy. On the other hand, we overwrite emails if you decide to backup from scratch or you backup the same interval you already backed up. For example, if Gmail changed something in some email (accidentally - deleted content of the email but kept its record ("name - ID") in Gmail, the program would download an empty email and overwritten the correct one in the local copy.
Second, the program backup "All mails" folder. According to our experience, it should contain all sent, received, and draft emails.