Where did you install Firefox from? Help Mozilla uncover 3rd party websites that offer problematic Firefox installation by taking part in our campaign. There will be swag, and you'll be featured in our blog if you manage to report at least 10 valid reports!

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

Cannot send emails - error code 5.5.1- cannot fix

  • 1 پاسخ
  • 1 has this problem
  • 1 view
  • آخرین پاسخ توسّط Matt

more options

One day my ability to send emails just stopped. The message said, "An error occurred while sending mail. The mail server responded: 5.5.1 Invalid command. Please verify that your address is correct in your account setting and try again." I have checked everything I can and have not discovered any incorrect information regarding the email address. I am able to receive emails as always. What should I do to be able to send emails again. (Can send emails on two Kindles and my desktop computer).

One day my ability to send emails just stopped. The message said, "An error occurred while sending mail. The mail server responded: 5.5.1 Invalid command. Please verify that your address is correct in your account setting and try again." I have checked everything I can and have not discovered any incorrect information regarding the email address. I am able to receive emails as always. What should I do to be able to send emails again. (Can send emails on two Kindles and my desktop computer).

All Replies (1)

more options

In order for us to better investigate this issue you need to add a little more non-personal information.

Please add the troubleshooting information to your post To find the Troubleshooting information:

  • Open Help (or click on three-line-icon and select Help)
  • Choose Troubleshooting Information
  • Use the button Copy to clipboard to select all. Do not check box "Include account names"!
  • Paste this in your post.

Please also add the result of these troubleshooting steps to your post

  • Does Thunderbird work in TB Safe mode (see Thunderbird Safe Mode)?
  • Do you use anti-virus and firewall software? What is the version?