Strangely, the mail does come in, but it is as if the phone is schizophrenic. For almost a month it has reported "Updated on 6/12/21", even though I have received mail timestamped eight minutes ago.
A frequent error when I check email where there's no wifi and weak cellular signal is "This message cannot be displayed because of the way it is formatted. Ask the sender to send it again using a different format or email program." The message in question I wrote on this same iPhone half an hour before in an area with strong cellular coverage. I have no idea whether that has any effect or not.
I should say I have closed Mail and tried again. I have also done Restarts periodically with no evident change.. Thanks for your suggestions! Any more ideas?
Cheers,
Kit