How to restore email

We switched our mail server to Office 365.
In the eM client, the existing account has been deleted to create a new account.
Is there a way to restore the old account?
Unfortunately, when we switch to the new server, we are missing all mails in the sent folder!

Does the eM client an automatic backup?

eM Client has an Automatic Backup, but it is not enabled by default.

You can check in Menu > Settings > General > Backup and see if you enabled it. If you did enable, you need to also check how many of the past backups are preserved. If it is set to only one, and a backup has been made since you removed the account from eM Client, then the sent messages will not be in the backup.

Another option may be if you backup your hard disk. It may be possible to recover your sent messages from that.

thank you for the info,
If no backup has been set up, are the mails lost?
Arethes not stored in a profile, similar to outlook?

For IMAP or Exchange accounts, the messages are stored on a server, not on your computer. eM Client maintains a cached copy of those messages, but if the account is removed then so is the cache.