Ahh. Interesting!
Step by step so I don't forget what I did:-
1) I changed both, as you suggest. I also changed the robertos SMTP selection to O2 SMTP.
I tried a send from robertos and got
Sending of message failed.
An error occurred sending mail: SMTP server smtp.o2.co.NIX is unknown. The server may be incorrectly configured. Please verify that your SMTP server settings are correct and try again.
2) I corrected the O2 SMTP address.
Sent from robertos via O2 SMTP server with no problem.
Header on the received email is via O2 and no mention of Tsohost servers.
3) Altered personal domain SMTP selection to normal and saved just to clear any wayward setting. Then re-selected the O2 server that works on robertos and saved again.
Error message as above with the Tsohost (personal) SMTP server name instead of "o2".
4) Set the robertos SMTP server to be the default instead of the personal one.
Robertos still sends fine via O2.
Odder and odder!
5) Now, the net result of the above is that both robertos and the personal are set to use the O2 SMTP server, but the default server (which should really only alter what is initally selected at new account setup time) has been changed from the personal to robertos.
A send from the personal goes via robertos SMTP server (which is on Tsohost), not the O2 one that is selected.
6) Corrected the personal SMTP server but didn't select it.
Sends via robertos.
7) Select and save personal SMTP server on the personal domain.
Sends via robertos.
8) Reset the default to the personal domain server.
Sends correctly.
robertos sends via O2
9) Select personal SMTP on robertos account.
robertos sends via personal.
10) Select robertos SMTP server on robertos account.
Sends via robertos SMTP
My conclusion from the above is that TB on the personal domain account is always using the
default SMTP server, and ignoring the selection in its setup screen.
The two unique things that spring to mind are that it was the first account set up and it is also the first in (so far as I can ascertain unsortable) list of accounts/folders on the left.
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost.
Internet connection - O2 Standard.