Emails on IPhone going into Junk

I’ve recently noticed my emails from work are going into my junk folder

my company has recently changed their email address, and this is when the problem started….

I have moved emails from my junk back into my inbox and also entered the new email addresses into my

contact, but no change.

I’ve also noticed emails will flash up on my notifications, but when attempts are made to open, the email has disappeared and may only re materialise after a few hours or even the next day

can anyone advise and or offer any solutions …..