I have just set a read request on a message and sent it, and then looked at the copy in my Sent folder. Even when opened with ctrl+u, which exposes the "source", there is no sign that a read receipt was requested.

I used two accounts which I trust not to swallow read requests, and I did get a prompt to reply with a read acknowledgement. Some, providers, notably gmail, don't forward the read request to the recipient.

I believe the read request goes into the so-called "envelope" which we end users don't ordinarily get to see.

I think the answer is "no".

I too have just performed a similar test. I notice that the source of my message included a "Disposition-Notification-To" field which was set to my email address. I believe this to be the indication that Return Receipt was requested. Thunderbird therefore DOES know that a Return Receipt request was made.

What I'm looking for is some means of seeing that the request was made whilst viewing the list of Sent emails e.g. a column similar to that which shows that an email has an attachment.

Yes, just found that one too. I thought it was specific to DSN (Delivery Status Notification) but no, wrong, it is part of the Read Request.

Do you get much value from this? Few users respond to read notice requests, and many email providers remove the request altogether.

DSN is even less successful - most servers have it disabled.

You could...

Create a custom filter field for the "Disposition-Notification-To" header. Set up a filter to act on this and apply a tag, so that the colour and/or tag name tell you what's going on.

We can now apply filters to Sent messages, so once set up it should be automatic. As a one-off, you could manually run the filter on your current Sent items.

You asked: "Do you get much value from this?". I have to say it is not something I would need to use every day. However it can be helpful if I have not received a reply that I was expecting. If I knew that I had requested a receipt then knowing that the email had been read would be valuable information in understanding the situation (I found out just today that an email I sent a week ago had not been read since the recipient had problems with their email server and had never received it.)

You mentioned that "few users respond to read notice requests". I have to say that is not my personal experience; but perhaps that is in the nature of my contacts. Personally, when I receive an email with a Read Request I assume it is important to the sender that he gets the receipt otherwise he wouldn't have asked. It's no great problem for me to oblige him.

NB: I would agree that requesting receipts by default is counter-productive. I only use them when the message is particularly important to me.

Do you always want to send a 'Return Receipt' with an email ? OR only for a particular mail account. If yes: via Menu bar: 'Tools' > 'Options' > 'Advanced' > 'General' tab OR via Mail Toolbar: 'Menu icon' > 'Options' > 'Options' > 'Advanced' > 'General' tab click on 'Return Receipts' button.

select 'When sending messages, always request a return receipt' make any other selections and click on OK Click on OK

These options can also be set in Account Settings: via Menu bar: 'Tools' > 'Account Settings' OR via Mail Toolbar: 'Menu icon' > 'Options' >'Account Settings' Or right click on mail account name in Folder Pane and select 'Settings'

select 'Return Receipts' for the mail account. You can use the global preferences option as explained above OR you can customise for that account.

This might be useful if you always want to request a Return Receipt for one particular email address/mail account, but not all.

click on all OK's when finished.

Thanks for your input but, as explained above, I do not wish to request receipts by default to anyone.

I guess in the absence of a way of displaying this info on the Thunderbird UI I will simply have to view the message source and look for a "Disposition-Notification-To" field.

So you are not interested in the Tagging option I outlined? That would give you a visual cue as to when messages had a Disposition-Notification-To header field.

I will certainly give it a try. Thanks.

I am finding that tagging is not reliable. A Saved Search folder using the same detection criteria works well though.

As always, YMMV.