usually it is because the senders name is inserted into the message as a display name and the list email address. This is very common

So what you see in your list of mails is "Susan Brady", but the From email address is list@mysubscribedlist.com

The address an email replies to is decided based on the information in the message header from the sender.

Normally the From: header is used, but as I said earlier, what you see and what it contains can be two different things. The following is the from header information from a mail I sent.

From: Matt Harris <devilsgatedrive@gmail.com>

In the case of mails from Blogger, I see an email like From: edwardpitt <noreply-comment@blogger.com> so Thunderbird tells me edwardpitt made a comment (spam) but the email address is not Edwards.

If for instance I had setup a reply to for that devilsgatedrive account to the following

Reply-To: unicorn.consulting@gmail.com

When you clicked reply the address would show as the reply-to address not the from as it takes precedence . Reply-to is frequently set by mailing lists to stop people accidentally taking the conversation off the list. If you with to make personal replies as well as list replies the reply all button is perhaps a better starting point so you get to remove any unwanted addressees but Thunderbird will collect everyone from the from: and CC: lines of the email.

BTW, I have no idea what you mean by "not with Return-to or Sender" as they are not email terms.

Hi. Matt, Thank you for your prompt reply! Getting your generous support is very reliable for ordinary users like me.

Now, it seems that it may not be transmitted well because of my poor English ability, so I will write the problem again. Firstly, I have to correct "The mailing list account is included in the reply destination, not with Return-to or Sender." to "The Reply destination of the message is got any mailing list address instead of Reply-to or Sender address.", Is it rightly transmitted?

Okay, The phenomenon occurs in Ver68.10 and before.

Supposing a message comes from n@xcompany.com. The recipients of the message are not only my address, but also several mailing list addresses. (e.g. myaccount@somecompany.com, other@somecompany.com, list1@somecompany.com, list2@somecompany.com ...etc) Then, when I select the reply command to the message, the address of a specific mailing list(e.g. list2@somecompany.com) will be set as the default destination address by message creation. I expect the destination to be set to n@xcompany.com.

Sincerely, Yohsinon.

I would agree that a 'Reply' (not 'Reply All' or 'Reply List') you would expect the TO to be n@xcompany.com.

But it really depends upon what has been set up by sender and assuming n@xcompany.com was the real sender. It is possible, the From says n@xcompany.com, but maybe there is other instructions in the background. Have a look at the 'Full Headers' in the source to see what is going on.

select email and click on the 'More' button and select 'View Source'. It will open in a new window.