Mail administrator refuses my emails.
Somehow this happened: Some of my emails sent or replied to are not received by the person I'm sending them to. Instead a message from Mail Administrator informing me there was an error.
As these sent emails from me are to persons well known and in regular communication, I know their addresses have not changed or that they would certainly not be refusing them. They actually DO go through on another computer which I've had to resort to.
Oddly enough, most sent emails actually go through to others but those few are returned. I'm sure there must be some small adjustment I should make within the computer to remedy this, but I don't know what. Thanks for any help.