We're calling on all EU-based Mozillians with iOS or iPadOS devices to help us monitor Apple’s new browser choice screens. Join the effort to hold Big Tech to account!

This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

Comcast smtp verification failed.

  • 1 reply
  • 1 has this problem
  • 1 view
  • Last reply by sfhowes

GrammieRee
GrammieRee
more options

Have used Thunderbird for some time now with NO problems. Then I received a notice from Comcast (xfinity) that I needed to change my password, so I did. Deleted old password in Thunderbird and added new one. (Yes, I'm sure it is correct, I've put it in numerous times..) Receiving comcast email just fine but when trying to send I get this error message: Sending of username did not succeed. Mail server mail.comcast.net responded: [AUTH] Authentication failed. Thunderbird gives me the option to Retry, Enter New Password or Cancel. I've tried them all. I've deleted and reentered the new password in Thunderbird repeatedly. Comcast says my SMTP port should be 587 or 465 if needed. Was set on 465 but have tried them both. I've tried choosing no authorization for SMTP instead of 'normal password' and receive this error message: An error occurred while sending mail. The mail server responded: 5.1.0 Authentication required. Please verify that your email address is correct in your account settings and try again. No matter what I try, I still am unable to send comcast email via Thunderbird. Please help! Mail provider: Comcast (xfinity) Firewall/Antivirus: Norton security suite (provided by comcast) OS: Windows 7 Home Premium 64-bit Version: Thunderbird 60.0b10

Have used Thunderbird for some time now with NO problems. Then I received a notice from Comcast (xfinity) that I needed to change my password, so I did. Deleted old password in Thunderbird and added new one. (Yes, I'm sure it is correct, I've put it in numerous times..) Receiving comcast email just fine but when trying to send I get this error message: Sending of username did not succeed. Mail server mail.comcast.net responded: [AUTH] Authentication failed. Thunderbird gives me the option to Retry, Enter New Password or Cancel. I've tried them all. I've deleted and reentered the new password in Thunderbird repeatedly. Comcast says my SMTP port should be 587 or 465 if needed. Was set on 465 but have tried them both. I've tried choosing no authorization for SMTP instead of 'normal password' and receive this error message: An error occurred while sending mail. The mail server responded: 5.1.0 Authentication required. Please verify that your email address is correct in your account settings and try again. No matter what I try, I still am unable to send comcast email via Thunderbird. Please help! Mail provider: Comcast (xfinity) Firewall/Antivirus: Norton security suite (provided by comcast) OS: Windows 7 Home Premium 64-bit Version: Thunderbird 60.0b10

Chosen solution

They say the correct settings for the outgoing server are: smtp.comcast.net on port 587, STARTTLS security, authentication = normal password, and User name = full email address. If you still get errors with those settings, there is probably something else causing the problem, such as Norton, a VPN etc.

Read this answer in context 👍 0

All Replies (1)

sfhowes
sfhowes
  • Top 10 Contributor
more options

Chosen Solution

They say the correct settings for the outgoing server are: smtp.comcast.net on port 587, STARTTLS security, authentication = normal password, and User name = full email address. If you still get errors with those settings, there is probably something else causing the problem, such as Norton, a VPN etc.