How do you add your multiple addresses to your message?

Thunderbird works best with one per line. We have two addresses here separated by spaces and a comma, and there is a space just after "...bakker"

‘"harryrozeboom@upcmail.nl , hemmyrozeboombakker "@upcmail.nl’

It looks as if the comma has been recognized as part of the email address, as it has enclosed it all in quotation marks, and then it is puzzled by the "upcmail.nl" part left over.

I see what you mean but that's the message I get back. Each address is placed in a separate " To" box (the way TB works) and then I try to send but then I receive the error message. How does TB present the multiple addresses to my provider?

If I manually type the address into the To box and then the second one in a separate To box, it works fine. So the quotation marks are the problem? Why are the addresses placed between quotation marks? I normally use my Personal Address book and click on an address to have it placed into a To-box.

Turns out that the problem was with my Address book which was not correctly filled. Your answer put me on the right path and I thank you for it. Consider the problem solved. Regards, Harry Rozeboom.

Any spaces in the entries in your address book? Leading and trailing spaces can cause interesting issues.

The RFC states that multiple RCPT TO: addresses should be separated by commas, so the comma is not surprising if that is taken from the envelope. You can use commas in the address box in Thunderbird, but doing this breaks the address validation system.

Short of observing the flow using wireshark or similar, I don't know how to check what Thunderbird puts into the envelope. I may try that sometime.

But I'd expect commas.

Ah! You beat me to it. Well done.