I’m having a problem with just one email chain. The email has gone back and forth between parties for a few weeks. Nothing too wordy, no pics or attachments.

Replied to this email chain Friday and pressed send, left outbox but didn’t arrive other end. Tried various combinations of people and formats.

Can send to gmail but when tried to send it back it left gmail but didn’t arrive.

Made plain text but still left outbox but didn’t arrive other end (Note why does outlook insist on retaining email address link although I change to plain text? Is it not truly plain text?)

When outside party sends email in same chain we do not receive. They create new chain and still not received.

ALL other emails sent and received as normal

No AV, no firewall, no size limit (and now no hair)

Any ideas please? Pieter