How to transfer mail inside Google Apps?

Question

Google

Tell me, if there are adequate services with which you can transfer mail (and preferably everything else) inside Google Apps? I've tried some of them:
https://www.syscloud.com
https://spinbackup.com/
https://www.backupify.com/
spanning.com
None of them provide the ability to do this in any adequate way. Someone throws all the letters in a crowd in the inbox, someone beats the encoding. They don't have any convenience.
Are there any other options? (Outlook does not fit)

Answer 1

Documents can be transferred from account to account. Here's a tip for transferring ownership.
And here is a help on transferring the rest of the data, including mail.