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Mailing Lists not working in Thunderbird 78.4.0

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In previous versions of Thunderbird, I used to type the Mailing List name in the To, CC or BCC fields, and it would appear in the format: Mailing List <'Mailing List'>, and then when I sent the email Thunderbird would insert all the email addresses from the mailing list and send the email. In Thunderbird 78.4.0 it appears in the format Mailing List <Mailing List> (i.e. without the single quote marks) and sending the email gives the error message:

An error occurred while sending mail. The mail server responded: 5.1.3 The recipient address <Mailing List> is not a valid RFC-5321 553 5.1.3 address. z15sm5942088wmk.4 - gsmtp. Please check the message recipient "Mailing List" and try again.

The same error occurs if I open the Contacts Sidebar and select the Mailing List from there. It does appear to work correctly if I select the Mailing List in the Address Book, and then click Write to start a new email, but that cannot be used for forwarding an email (which I often need to do).

Is this a known bug, and is there a workaround?

In previous versions of Thunderbird, I used to type the Mailing List name in the To, CC or BCC fields, and it would appear in the format: Mailing List <'Mailing List'>, and then when I sent the email Thunderbird would insert all the email addresses from the mailing list and send the email. In Thunderbird 78.4.0 it appears in the format Mailing List <Mailing List> (i.e. without the single quote marks) and sending the email gives the error message: An error occurred while sending mail. The mail server responded: 5.1.3 The recipient address <Mailing List> is not a valid RFC-5321 553 5.1.3 address. z15sm5942088wmk.4 - gsmtp. Please check the message recipient "Mailing List" and try again. The same error occurs if I open the Contacts Sidebar and select the Mailing List from there. It does appear to work correctly if I select the Mailing List in the Address Book, and then click Write to start a new email, but that cannot be used for forwarding an email (which I often need to do). Is this a known bug, and is there a workaround?

All Replies (3)

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Does your list have a space in the name, and if so, does replacing spaces with underscores eliminate the error?

Check also that none of the addresses in the list have leading or trailing spaces.

https://stackoverflow.com/questions/62161786/553-5-1-3-the-recipient-address-is-not-a-valid-rfc-5321-address

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Unfortunately this does not help. I created some test mailing lists including both having no space and having an underline in the name. I now get the error message:

An error occurred while sending mail. The mail server responded: 504 5.5.2 <Test_underline>: Recipient address rejected: need fully-qualified address. Please check the message recipient "Test_underline" and try again.

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Did you check that all of the contacts in the list have a correct address with no formatting errors? I've sent a test message to a list directly from the Write window without errors in 78.4.