Comcast send mail issue

First thing to do is confirm that you're using the correct server settings; My working Comcast SMTP settings are:

SMTP (Outgoing): SMTP Server Name: smtp.comcast.net Port: 465 Connection Security: SSL/TLS Authentication method: Normal Password OR OAuth2 User Name: <my email address>

How do your settings compare?

The error message implies that it's either wrong settings or a temporary condition on their end. How long has this been going on?

What anti-virus/security/VPN software do you use, if any? They are all notorious for interfering with communication with email servers. You can test this by temporarily disabling them.

Yes SMTP setting are correct.

I've had this for a few months. I've been using comcast email browser on their web site (I'm lazy and busy at the same time).

VPN is AURA

Turn off the VPN and see if that improves things.

I turned off the VPN and got this response: Sending of the message failed. An error occurred while sending mail. The mail server responded: Please ensure your email address and authenticating user match when sending messages. Please verify that your email address is correct in your account settings and try again.

Are you using OAuth2 as your authentication method, or Normal Password? If OAuth2, follow these steps to be re-authenticated:

- Make sure that you have cookies enabled in Thunderbird (see <Settings | Privacy & Security | Web Content | Accept cookies from sites>;

- Delete any saved cookies for Comcast (see <Settings | Privacy & Security | Web Content | Show Cookies>);

- Remove any existing entries for this account in Saved Passwords (see <Settings | Privacy & Security | Passwords | Saved Passwords>);

- Restart Thunderbird, after which you should be prompted to re-authenticate.

I'm using normal password.

I will try doing what you suggest and see if that works.

The method I described only works for OAuth2. Comcast seems to have introduced that authentication method a year or so ago, but never bothered to tell anybody. As far as I know, either method should work. It wouldn't hurt to try OAuth2 - it's better, more secure. You can always go back to the other if you need to.

I am going to change to OAuth2 Thank you

According to Comcast I am SOL. What a pain. Thank you.

Is that what Comcast told you? Did they give a reason? I can think of no valid reason Thunderbird can't be made to work with their email service. I mean, it works very well for me and for many people I know in this area (Massachusetts) who use it. I've had more than my share of problems with them over the years, but I have to say that their email service has been generally solid and well-behaved for me.

I still suspect Aura. I see that, besides their VPN service, they also have various other ad blocker and virus "protection" features. Those should all be temporarily disabled to test whether they are the problem. If you restart Windows in Safe Mode With Networking, that will do just that and allow you to test.

I will try that tomorrow. Thank you.

We have two errors here.

1. Your VPN is masking how you connect to the internet. YOur mail provider insists that to use their mail server you will connect to the internet using their service. This is a conflict that can usually be bypassed by excluding Thunderbird from the VPN.

2. You are sending mail using the wrong username in you login. Like all good fairy tales this one starts with once upon a time.

Comcast and some other US based internet service providers decided that if you sent mail it would be sent via their mail server and did just about all they could to force that to be the case. I some cases to the point of blocking normal mail sending ports from transmitting mail anywhere but their mail server. The result was that they were sending mail for yahoo and any number of business servers

Fast forward a couple of decades and they now not only discourage this, they outright refuse to allow it. So when you send mail from billy@comcast.net, the username logging into the SMTP server has to be the one Comcast allocated to the Billy mail account. This has been complicated by Comcast now having a migration to Yahoo for mail accounts on offer

Before proffering any advice regarding Comcast it is necessary to know if you are a legacy Comcast mail user (which I think Lin has assumed) or are now a yahoo mail user with a Comcast email address. See https://www.xfinity.com/support/articles/yahoo-email-migration-overview