Right-click the yahoo account in the Folder Pane, Settings. Is the Your Name entry correct? Click Edit SMTP server in the lower right pane. Is the outgoing server smtp.mail.yahoo.com, with the same User Name (email address) as the selected account in the left pane?

Thanks for your quick reply. Unfortunately this has not resolved my issue. When I click settings as you suggest the name is the same as on the folder pane. Maybe further info might help. I have two yahoo accounts; the problem is only with one of those accounts, the one with which I signed up with Garmin. When I receive a message in this account the recipient (the "To" instead of the "From) in the email heading shows as Garmin; when I right click on Garmin, then View Contact it shows Garmin as the name and when I then click View Details it shows only Garmin as Display but no first name or last name and it does not let me make any change and there is no edit button; so I'm stuck.

Right-click the affected account, select Account Settings. What does the Your Name field contain? It should contain your name as you want it to appear to recipients of your messages.

Thanks for your reply. There is no Account Settings when I right click on my email account in the folder pane. When I go to Tools, Account Settings, and select the affected account it shows my name, not Garmin. Here is some more information: When I receive a message in this account the recipient (the "To" instead of the "From) in the email heading shows as Garmin; when I right click on Garmin, then View Contact it shows Garmin as the name and when I then click View Details it shows only Garmin against the Display box but no first name or last name and it does not let me make any change and there is no edit button; so I'm stuck.

If you receive a message and the recipient (you) is 'Garmin', that is what the sender associates with your email address, and makes sense if the message comes from Garmin. Your original question implies that messages you send from the Yahoo account are appearing to recipients as coming from 'Garmin', which is not possible if Your Name for the Yahoo account is 'jymaillat' or similar.

Thank you for taking the time to reply to my question. It's not the sender who associates my name with Garmin; I checked on my wife's computer for the messages she sent me and her system shows the recipient (me) with my name, not Garmin, so it's my system (Tbird ?) which switches it to Garmin. I was wrong in stating that when I send a message it appears, at the other end, as coming from Garmin; I'm sorry I created confusion with this wrong statement. As I mentioned in a reply to another person (I don't know whether you see them or not), when I receive a message in the problematic account and it shows Garmin as the recipient I right click on Garmin, then I click View Contact and it shows Garmin as the name and when I then click View Details it shows only Garmin against the Display box but no first name or last name so i think that that's where the problem is but it does not let me make any change and there is no edit button in this window; so I'm stuck.

If you receive a message and the recipient is identified as Garmin, that can only be changed by the sender, which explains why you can't change it.

I just went on my wife's computer to send myself a message. Garmin is not accepted as a valid recipient and when I type my name as a recipient it shows my name and there is no sign of Garmin anywhere so this is not the issue. The problem is definitely on my side. The issue is that when a message arrives for me on Tbird the system displays Garmin instead of my name while on the sender's side it does show my name as the recipient and not Garmin. So this is either a Tbird or a Yahoo issue.

How does the sender change this when Garmin appears nowhere in their system ?

If what you say is correct then how do I make the change when I send an email to my problematic email address from one of my other emails addresses where I am therefore the sender ?

If what you say is correct then how do I make the change when I send an email to my problematic email address from one of my other emails addresses where I am therefore the sender ?

Simple. In Thunderbird's Account Settings (for one of your other accounts), change the Your Name field to something else. Like I said earlier, the name that this field contains is what the recipient sees in the "From" field. For testing, change that field for one of your non-problematic accounts, then compose a test message and send it to the problematic or your other account. While composing, you'll see the From field shows what the Your Name field is currently set to. When the message arrives, the recipient should see the "Your Name" entry in the From field of the message.

Note, however, that the From field in Thunderbird will show the name of the sender as saved in the address books. So, if the sender is saved as "Jane Doe" in your Tbird address books and you change the Your Name field to "John Doe", the recipient will still see "Jane Doe" as the sender's name. You can bypass this by opening the message in an environment where the sender's address has not yet been saved using a different name. In my testing, I saved the message as an eml file (TBird File menu > Save As > File > Save As type > Mail Files) and opened it with Outlook and the Windows 10 Mail app. The From field showed exactly what I had entered in the Your Name field in Tbird.

The problem is resolved; it so happens that when I signed up for Garmin (and for Fitbit for my wife) I gave our respective email address and the system created two contacts in the Contacts app, one contact under Garmin and one under Fitbit with our respective email address. I realized this when I went into Contacts and searched for Garmin and Fitbit ; I then deleted those two contacts and the problem was resolved. So I think that what happened was that, for some reason, Thunderbird was apparently defaulting to my email address under the Garmin contact rather than under my actual contact and my wife's email address under the Fitbit contact rather than under her actual contact. I just checked by sending a number of test emails to/from my respective accounts and from my wife's account to me.

Thunderbird uses your address book entries to allocate names in the message lists. This means that whatever is held in the address books for You@youremail.com will appear in Thunderbird's user interface. The logic being you named your contacts, so it is more friendly to display the name you chose.

Personally I turn that option off as confusing.

Go to options and turn of the display option "Show only display name for people in my address book".

Good suggestion Matt. Thanks. I'm still puzzled, though, as to why T'bird picked my email address from the Garmin contact listing as opposed to picking it from the listing under my name which has the same email address; because, alphabetically, the Garmin contact listing came before the listing under my name ? We may never know. Anyway, the key is that my problem has been resolved.

That's a possibility. Imagine you were developing Thunderbird and you have a scenario where the same address is saved twice using different names. Which name would you pick when displaying that contact? What logic would you use to pick a name? I would query the database, sort the resultant data set, preferably alphabetically, then pick the first instance of occurrence. It's a logical dilemma that must be solved one way or another.

Unfortunately, TB has a bigger problem in this regard. I receive quite a few emails that come from "donotreply@wordpress.com" but from different organizations or newsletters. When I look at them on gmail, the sender information is accurate, but when they download into TB it assigns, seemingly at random, one of the possible users of a "donotreply@wordpress.com" account as the name of the sender. This makes it impossible for me to properly sort through my emails according to the actual sender. And because all of these accounts seemingly have "the same" email address, there is no way to add them to my address book or provide TB with any more guidance on what name to use. Changing the checkmark by "Show only display name" doesn't help because these aren't in my Address Book (and can't be for the reason described above).

Any idea how to fix this?? Only seems to be a problem in TB, not in other mail clients.