Hello nancyfromharwich,
Thanks for providing us with those additional details. Next, can you please tell us when you first encountered this issue and if you have made any changes to the settings on your iPhone or the Mail app? Also, can you please tell us all the troubleshooting steps you have taken so far in an attempt to resolve your issue so that we can avoid repeating them? When possible, please be specific when describing the steps you've taken and the outcome after each step. Lastly, please tell us the version of iOS you are currently running on your device, and we'll continue from there.
Find the software version on your iPhone, iPad, or iPod
Thanks for using the Apple Support Communities.
Cheers!