I am thinking there are issues with spectrum again. does your user name still contain your road runner email address or have the smart people changed your user name and now refuse mail because they did that?

Thanks, Matt. I see that my user name is just billward, so I changed it to billward@kc.rr.com. Then I sent a test message and got the same "Send message error". Do you have any other suggestions?

I see that my reply to you went through. That's even more confusing.

Matt, I still cannot send email using my roadrunner address. Can you offer any other suggestions or refer me to someone who can? Thanks. When RR sent me the "Send message error" message, they referred to AUP#Out-1500. What does that mean?

I haven't heard any further word about a possible solution to this problem. However, I want to let the community know that the problem mysteriously was solved yesterday without my doing anything further. I can now send emails using my roadrunner address and they go through just like they used to. Someone must have taken action to correct whatever the problem was. Thank you.

I had this exact problem recently and fixed it.

The problem: When you hit the send button, an error message says, “Sending of the message failed. An error occurred while sending mail. The mail server responded: [your email address] send rejected. The email address you are sending as must match the email address you used to auth. Please check you SMTP settings. AUP#Out-1500. Please verify that your email address is correct in your account settings and try again.”

Probable cause: If you have multiple accounts with the same provider, a Thunderbird update has applied the same outgoing server info to all. In my case, I have four email accounts with Spectrum, formerly Time Warner Cable. Sometime between December 14 and 20, one of the four was made the “default”, so it’s info was reported to the server, even when I was trying to send from one of the others. I was suddenly unable to send from three of my accounts.

How to fix this: Amazingly, it’s not under “Server Settings.” In the left hand panel, right click on the problem account name and choose Settings. At the bottom of the main page, you’ll see the wrong email address in the Outgoing Server box. DO NOT change this yet, because it will simply make it the new “default” (I tried this first).

Instead, scroll to the very bottom of the left hand panel to find OUTGOING SERVER (SMTP). When you click it, the main screen will show the default account. Click ADD to add the outgoing server information for your problem account. In my case, it was identical to the default, except for the user name. Go back to the left hand panel and click on the problem account. In the Outgoing Server box, there will now be a drop-down list where you can choose the correct info.

After taking these steps, I had to enter my password (clicking the save password box) the first time I sent a test email. Hope this helps someone.