I have Read Receipts disabled, but one was generated when MY address is in Disposition-Notification-To

It is possible for spam messages to create that perception as an attempt to bypass spam checkers. Thunderbird will not send you a message on its own.

Thanks for the response. However, if this Read Receipt was not generated by Thunderbird, the only other explanation is that it was generated by Microsoft's servers. It arrived shortly after I read the original spam message and was sent to my mail server (Microsoft) and delivered to my inbox. (And the headers show no "Received:" lines other than Microsoft servers). I still think the most likely explanation is that this is a bug in Thunderbird. Is there a more appropriate place to report this issue? I can provide the entire spam message - and the read receipt that was generated. Thanks.

You can report it at bugzilla.mozilla.org, but you need to be sufficiently specific so that it can be investigated. You're asking from where a spam message came, and that is quite vague.

OK. Thanks. I'll look into bugzilla. However, I'm not asking where the spam message came from. I'm asking about the Read Receipt that was generated when I read the spam message.

re :Thunderbird generated an email (to me) and sent it to my mail host.

No it didn't. That's impossible. I've had loads of these types of emails in various formats over the past couple of decades. It's just a spam email from an unpleasant person.

Some nefarious person had sent you an email and altered the data so it looks like it was sent by you. They do that because it gets past the spam filters - after all you are not going to setup your own email address as spam nor are you going to mark it as spam for same reasons. So in nutshell the sender knows it will get into your Inbox.

If you view the source code you will find it says something very different. The 'Received by' entry that's immediately above the from, to date subject headers is the first server and it probably implies the email was received from someone else maybe using a mailing service.

The 'Read Receipt' "Disposition-Notification-To" was generated by the person who sent the emails in the first place, they asked for it. That's what you would see if anyone asked for a 'Read receipt'. The sender is just trying to get you to either click on it or is hoping your email client setup would send an auto response to a Read Receipt. The sender is just trying to get an auto conformation that your email address is legit and live. There is no bug. Delete the email and then compact the folder to remove all traces of it.

Thanks for the response and explanation. However, I know all of this and I see no evidence that the Read Receipt message came from another server. It contains only three Received: lines in the message - and all three reference Microsoft servers ("outlook.com" specifically). So I see three possibilities:

1. Thunderbird generated the Read Receipt message when I read the original spam message
2. Microsoft generated the Read Receipt message when I read the original spam message
3. A spammer logged into a Microsoft mail server and forged a Read Receipt at the exact time I read the original spam message.

Option #1 seems the most likely to me. If anybody is curious, I can supply the entire Read Receipt message. (Or post it here if that is appropriate)

re :I see no evidence that the Read Receipt message came from another server. I would not expect the 'return receipt' you got in Inbox to come from another server because it was sent by you to you, because the spam person had put your email address as sender.

The 'Received by' header info etc that would be important would have been in the source of the spam email. That would have proved it was not you who sent it originally and it might have mentioned the IP address. It may also have shown any code etc to auto generate a return receipt' by way of another means.

Thunderbird can only generate the 'Read Receipt' under specific circumstances: A) if you manually clicked on 'Read Receipt' button in Spam email. B) In 'Account Settings' > 'Return Receipts' for the account, you have set up to auto return receipts. C) You have selected to use the global return receipt preferences for the account AND those global settings say 'Allow return receipts' as set as 'Always send'.

The only difference, is the return receipt normally would not be sent to yourself. However, if the spam email stated to do a return receipt to sender and it has you as sender then it means it was generated specifically from that original spam email. But do you still have that particular 'Spam' email ?

Do you have 'remote content' completely disabled? By default Thunderbird disables it, but some people do enabled it or enable it for specific emails etc.

2. Microsoft generated the Read Receipt message when I read the original spam message

It's a possibility because if you are using an Imap account then the server would know if you had read the email. Check out this in the outlook webmail account.

• Select Settings > View all Outlook settings.
• Select Mail > Message handling.
• Under Read receipts, choose how to respond to requests for read receipts.

What is set up?

Another query : Have you ever used Outlook email client on that computer ? I have seen a case where a user previously used Outlook and did not realise it was still operating in the background. In that users case, Outlook had a Pop account and it was removing downloaded emails off server. So in Thunderbird, user wanted to know why emails kept disappearing. In your case, is Outlook doing a similar thing - it's got a setting which is auto sending return receipts. OR another thought - do you use a phone to read emails and could that account be auto returning receipts ?

Yes, I still have the original spam email and yes, it came from an outside server. You mention a 'Read Receipt' button in the original email. Not sure what this means. I see no button or menu option to force a Read Receipt. I always thought that these were only generated by Thunderbird when I read a message (if that option was enabled). And, of course, I have that option disabled. In my Account settings (under "Return Receipts"), it is set to use my Global preferences. And my global setting is "Never send a return receipt". Right now, I'm left with two theories:

1. A bug in Thunderbird (still my favorite)
2. Some kind of Microsoft server shenanigans (always a possibility - considering how often Microsoft does things "their way")

I still haven't filed a bug report, yet. I may try to do that tomorrow.