First, Thunderbird does not have the ability to block email; it was never part of the design. If you are being blocked, it may be due to your desire to send email to 100 persons.

Thank you David for your repy. Sure I am in fault as I tried to send to 100 persons and I dont know it was not possible. But the question is NOW I am blocked and the FAI (Swisscom Bluewin) as already cancel the block and I can use normaly the mail on the FAI Swisscom Bluewin BUT NO MORE with Thunderbird that give me on each testing to send an error message with blocklist ?

I am not an expert on blocking, but if you send another message and receive a blocking message, please post it completely here and someone may be able to advise on where the block is coming from and how to remove it.

I have already indicated the full error message : Herewith the error message that block all my sending message.

L’envoi du message a échoué. Une erreur est survenue lors de l’envoi de l’e-mail : erreur du serveur SMTP. Le serveur a répondu : bluewin.ch mailout-004.p.bluenet.ch Swisscom AG sc774: Blocklisting in effect.

Puzzling. if Swisscom has lifted then block, why are you still getting blocks from them? I suggest contacting them. Again, I am not well-versed in blocks

I contacted again the provider Swisscom and they confirm me that no block list is on my account, therefore the blocking is in Thunderbird somewehre hiden ????

No. Please translate totally the message. Thunderbird is really just a dumb agent; it receives messages for you an sends messages for you.

The message is since one week always the same as undermentionned :

L’envoi du message a échoué. Une erreur est survenue lors de l’envoi de l’e-mail : erreur du serveur SMTP. Le serveur a répondu : bluewin.ch mailout-004.p.bluenet.ch Swisscom AG sc774: Blocklisting in effect.

The problem is that I'am no more able to send email with Thunderbird, I always receive the above mentioned error message. The problem is not by the FAI Bluewin Swisscom as when I try to use the Bluewin Swisscom page for email it works without problem and I can send email. Therefore is someting in Thunderbird who is always indicating blocking list but by Swisscom there is no more this blocking list as confirmed per phone and as tested on the swisscom email site where I can send email without problem !

It is not Thunderbird, but thunderbird is sending from your IP address, whereas when you send from website, you're using their IP address. Thunderbird has nothing in it to make decisions on whether to send a message or not. When you click the 'send' button, thunderbird launches the message into the internet and then reports whatever message is returned. The error message continues to show you who is sending the error - bluewin. it's right there in the message, so I am puzzled why you keep believing otherwise.

Hello David, I understand what you explain me. But whats about the fact that when I used the Swisscom Bluewin access I can free send emails as there is no blocking list in Swisscom Bluewin ! When I try to send the same email in Thunderbird I become immediately by clicking on send the error message blocking list. Do you understand that the problem is in Thunderbird and not in Swisscom ....

If the error message comes from Swisscom, the block also comes from Swisscom. That' their error message. They can deny it, but the messsage still comes from them. Thunderbird is completely ignorant on internet policies; it does what it's told to do and then reports back any error messages.