Signing into emails but getting different email addresses emails

We use an iPad at work for all our emails/calendars etc, today out the the blue our iPad just went dead. We’re desperately trying to access the emails, however, when I sign in using our email address and password I’m sent to an inbox with a few emails from a couple of years ago, and the the address is different...still something linked to work but not the email address I signed in with, and none of the mail (which we get several everyday) are there. I wasn’t working there when this was set up, so have no idea what was done. But it’s vital I can access those emails but if the emails address which everyone emails isn’t even opening the inbox those emails I’m not sure what to do! Help!