How many accounts do you have, how many smtp servers, and is each account set to send through an smtp with the same User Name as the sending account?

I have four accounts, four SMTP servers and each account is set up to send through an smtp with the same User Name as the sending account. But on two of the accounts, lets call them A and B, when I send an email using account A, it changes account B's SMTP user name to the same as account B's. So when I want to then send an email using account B, I have to go in and change the user name, and vice-versa.

Just to confirm, select account A in the left pane of Account Settings, then click Edit SMTP server in the right pane. Is the User Name in the smtp the email address for A? Select account B in the left pane and repeat. Is the User Name in the smtp the email address for B? TB doesn't change settings by itself, but some services like gmail will automatically switch the User Name to the one set in the smtp server, so if e.g. account A is sending through the smtp with B's User Name, recipients will see the message as sent from B.

What is happening is, if I use account A to send an email, then it sets account B's user name to account A's, and so then when I go to use account B, I have to change the user name back to the correct one.

I can't offer more advice until you confirm the question in my previous reply: is each account set to send on an smtp whose User Name matches the email address of the sending account? The smtp server is selected in the Outgoing Server (SMTP) drop-down in the right pane when the account is selected in the left pane of Account Settings.

I appreciate your efforts to help. What I am trying to tell you is that I can't set up the smtp correctly for each account, because when I put the correct user name into account A, it copies the same name into account B and vice versa. So I can't get all my accounts (of which I have four) to match at once.

In Account Settings, select Outgoing Server (SMTP) at the bottom of the left pane. You should have 4 smtp servers. If they are on the same server, they can have the same settings except for User Name (email address for account 1,2,3 or 4). Give each one a unique Description, e.g. smtp1, smtp2 etc. Add servers if necessary.

Select account 1 in the left pane of Account Settings, then click the Outgoing Server (SMTP) drop-down so smtp1 is selected. Select account 2 in the left pane of Account Settings, then click the Outgoing Server (SMTP) drop-down so smtp2 is selected. Same for 3 and 4.

As an extra step, remove the passwords from Saved Passwords in Preferences, so there are no mismatches. Restart TB and enter the correct account password when prompted, for each account.

That worked. Thank you so much for your time and help!!