iphone 12 pro has deleted hundreds of recent emails

I noticed firstly that when I clicked the arrow to reply to an email the screen wouldnt open for ages.

Then suddenly last night my emails went from thousands to 300 and the recents are all gone. only the really old from 2018 are there. I have tried switching off and on and ive gone in to the email and set no limits with fetch etc but still nothing. These are work emails and I really need to have them back on the phone