so what makes you think that the mail is not being sent. Failure of reception notwithstanding .

When Thunderbird sends an email it holds the connection open until the SMTP server send a acknowledgement that the massage has been received for transmission without error. Anything after that you will need help from Orange to explain what happens to your mail after they get it.

Just to be clear this is an SMTP issue, not a Thunderbird one and any attempt by your provider to decline support for Thunderbird only demonstrate ignorance by the person trying to get you off the phone. They supply the SMTP server, it has accepted the mail. Only orange can tell you what happened next with r3egard to their handling of the transmission.

Possible orange is listed as a spam source with other mail providers. I really can do nothing but guess.

Thank you Matt - I very much appreciate your explanation and time spent trying to help with the problem.

One of the reasons I wrote to Thunderbird support was because my French is very limited indeed, and I do not have the knowledge of the vocabulary to speak with confidence on the phone with Orange.

I have checked the settings and the port is the same on the main default account as those on the sub accounts. I have done another test a few minutes ago. Using Thunderbird, I sent the email from the main account to one of the sub accounts. As soon as I pressed 'send' the icon came up 'sending email' and the email appears in the 'sent' folder. When I pressed 'get all messages' nothing appeared in the address to which I sent the email.

I did the same test with the 'orange mail' account on the internet and sent an email from the main account to the same sub account (as with Thunderbird) and when I pressed 'get all messages' the email appeared on the Thunderbird email page.

So maybe this means that Orange is not the problem.

Sorry I seem to waffle on but I want to give you as much information I can to help further with the situation.

Best regards.

Hi Stick with trying to find out from Orange what their SMTP server is doing with the sent email. When you send email from their online webmail ('orange mail' account on the internet), it is not using SMTP - the method is quite different when you send from Thunderbird or any other client software. So testing from webmail is not relevant to the SMTP issue. You could try installing Windows Mail or Outlook or another email client, and test sending to the same SMTP address to prove it is at their end.