I have a problem in our company. We are using Exchange 2016 and a backup mail server from a different provider, as we were using this provider before we came up with our own server. We had a problem last week, when the server fell down, all the emails went to the old, backup server which is okay. But my question is: Is there any automatic way to let Exchange download to Exchange mailboxes all the emails that fell to old mailboxes during the drop-out of our server? We are hugely addicted to our emails and we don't want to let some emails be missing. Sorry for my english, thanks for help.
There is no native way in Exchange to do that. But as an idea (if your solution you build isn´t an "Backup MX" as mentioned here) you could use imapsync to download emails from the 2nd IMAP postbox and store it inside the Exchange mailbox from the users on your side. However the issue with the password might be something tricky and you might wish to implement something like written on the Microsoft website here and here and set up an delegation account.
POP3 Connector was introduced and removed in 2003 SBS, you could use any 3rd party software or configure pop3 on each outlook instance to download email from the external/backup server to your exchange server.
One of the better 3rd party utils: https://www.mapilab.com/exchange/exchange_pop3/
Here is a list of Backup & Recovery solution which will enable you to Backup your Exchange information store, to get in detailed check this link.
Thanks a lot to all of you, all your help give me new look to this problem in the end we are not going to buy any pop3 connector, we just agreed with our provider of our old server to configure that server as a backup and it should be okay than. But again, thanks a lot for your time and patience