Exchange 2013 send connector after provider switch started sending on behalf of.
We have a on premises exchange 2013 server.
we receive through a pop3 into the server via 3rd party software which is working fine.
then when we send out we have a send connector with the providers smtp details ( say firstname.lastname@example.org as send account)
our previous provider we sent email from email@example.com through the send connector and it was received by recipient from the sender "firstname.lastname@example.org"
we changed our provider - all settings are the same in the smtp bar the new password but now the email is received as from "email@example.com on behalf of firstname.lastname@example.org"
I have no idea why the change of smtp provider would cause this as surely this is controlled in Exchange
any help much appreciated