Go to the outgoing server (SMTP) entry in your account settings. I do not mean the little drop down in the bottom of an incoming account identity. I mean the one in the list of accounts. Usually at the bottom.

Make sure you have an entry for each of your accounts. I am guessing you need to rename some so they actually have the appropriate email address in the name and add even more. I assume you are chasing one entry round and round instead of multiple SMTP server entries for multiple accounts/Identities.

Matt - Thank you for your quick response. I thought I answered but it may not have gone so I will try again. I followed your suggestion and went into the Outgoing Server section at the bottom of the account settings. I couple of accounts were missing and I added them. In this section, when I select each account and check the details below the list, everything looks OK. However, when I go into each individual account of the three accounts that are at issue, the User Name is still incorrect. For instance, in the account for "commercial" if I change the user name to commercial@korufarm.org that name populates to the other two accounts. (See attachments) I did reboot to ensure the changes were saved. By way of context, I have 4 laptops and a desktop and Thunderbird is set up exactly the same on each. When I set up a new computer I copy the profile from one of the others. Needless to say, I have the same issue on all of my computers so I can only guess that there is an issue with the profile. Again, thank you very much for taking your time to try to assist. It is appreciated. If you're someone who likes figuring things out, further suggestions always welcome.

Suggestion: In each SMTP setup, enter the explicit email address in the 'Description' field. Do this for all of them. Then, repeat the process of verifying accounts to SMTP settings and it will be clear which SMTP server is selected.

David and Matt - Thank you again. Perhaps I am not explaining the issue in an intelligible manner. Under the bottom Outgoing Server (SMTP) section each account is correct, has the proper description, Server Name, Port User Name, Authentication Method, and Connection Security. There is only one, I say again, one Server Name: mail.korufarm.org. It is the same for each, presumably because that is the name of my domain. However, for the last three accounts in the list, when I go into the settings for the account, the same User Name is in each of the three accounts. If I change the User Name in one so it matches the account, it instantly changes the other two to that name. Somehow, they seem to be linked at the User Name level.

After drafting the above I went to one of our laptops and deleted two of the three accounts that are problematic then added them again. The two are ones we use for non-personal purposes, Netflicks e-mails, etc, so no important data was lost. So far the new accounts seem to be OK so I will try this on the other computers. This may or may not be an interesting problem for your knowledgeable technical guys to look into. I am in my eighth decade so I am lucky I can find the power button. Thus, I greatly appreciate the time you both have taken to assist me. I have learned a lot from following your guidance. You are to be congratulated for sharing your time with we ordinary users. Greg

Thank you for your kind words. What you're experiencing is a situation we see here regularly, the seeming magical switching of server names, when the real issue is that multiple accounts are using the same SMTP server. That is why I emphasized giving unique names to Description field so you would recognize each one when setting the accounts.