Sometimes,for a variety of reasons,the customer service representatives' mail account can no longer used because of the banned old mail server.In this case,we must set up new pop/imap and smtp mail server in order to let the old mail account go on working.
However,after we've set up the new mail server and users can log in the mail system,you'll get the complaints from your colleagues that they lost some of the former mails from the customers.Yes,that circumstance exists if your colleague just not pull letters from the old mail server in their MUA before the time it crashed.In order to quiet down your staff,you may do as follows:
cp /var/qmail/mailnames/olddomain.tld/service/Maildir/new/* /var/qmail/mailnames/newdomain.tld/service/Maildir/new #copy & re-save
chown -R popuser:popuser /var/qmail/mailnames/newdomain.tld/service/Maildir/new
#take care to chmod directory permissions,for cp operation will make the owner to root
After the operations,you can notify your colleagues to receive letters from firstname.lastname@example.org now.And,the most important,contents include email@example.com that are 'lost' formerly complained by them.(the same to postfix)
Notice:In this example,two domains are on the same mail server.
If not in your case,please consider using scp or ssh,sftp in replace of cp command.