Lost nearly 2 years' worth of emails

Hello,

On the 21st Aug 2023, I suddenly noticed that my email box had changed on my iPhone and was displaying emails from 2021. At first I thought they were just being displayed in reverse order but I then realised they were missing (all emails from the 17/11/21 to 21/08/23). Checked bin, junk, archive, flagged etc but not there (also toggled read/unread etc). I tried closing down my phone, deleting the app and adding it again and nothing worked. I logged on to iCloud and it was the same situation there. I rebuilt my mail box but they are still missing. New emails arrived but weirdly some seemed to go to my junk when previously they wouldn't have.

I looked through these message forums but couldn't find anything that helped me. In the end, I gave up, but as time has gone on and I realise I am missing important emails such as guarantee for purchases or quotes etc, I have come back to the issue to see if there is anything left I can do to recover them. My phone is quite old (iPhone 8) but still I had no idea it could lose emails like this...

The only other thing I have just noticed is that just prior to this happening I had updated my SIM plan with ID Mobile.

Any help gratefully received.