Sounds like you have more than one email profile/identity in the same email client? If so, you need to check which one you are writing from before you send. Usually there is a small drop down toggle option somewhere at the top of the compose page where you can switch your identities by clicking on a down arrow and selecting the identity you want to send from.

Depends which email client you are using, but that option is available in both Windows Live email and Outlook. I have never used Thunderbird.

Many thanks for your help.

Do you know please if there is anyway to ensure that my domain name is always used without me having to check before I send each message?

Perhaps I can remove the gmail email address altogether?

You should be able to see which identity you are in when you compost an email by making sure you are in the correct identity's inbox. The sender will automatically be shown as being from which ever inbox you have composed the email from, unless you toggle it off and select a different identity in the toggle option before you send.

If you don't need the gmail address I would get rid of it. Trying to "unsync" Google accounts, particularly mail synchronisations, is quite confusing and in any event gmail does seem to duplicate emails in other synced accounts. If you don't need it my advice would be to close it to keep things simple.

Again Many Thanks for your help.

No problem. Can you kindly flag this discussion as resolved, so that the thread is correctly filed.