Is it possible to retrieve email setup in Iphone from previous employer?
There are a number of third-party utilities that allow you to browse through and extract the information stored in a backup of an IOS device. A quick perusal of those programs from a google search seem to show no mention of recovering email. All list SMS/Text messages, calendar, address book, notes but none mention email specifically.

Since most email on the IOS device is set up as IMAP the email is actually stored on the server. Perhaps the backups that iCloud or iTunes make doesn't include this cached data? I am unsure of this but from my cursory search it does not look good.

You may want to find the support pages of some of these tools (iExplorer is a popular tool) and ask that question there. Otherwise it doesn't look good.