Outlook Server Response 550 Access Denied 0x800CCC78

In this guide learn how to Fix Outlook Message Could Not Be Sent Server Response 550 Access Denied 0x800CCC78. This behaviour can occur because the SMTP server is not available for outgoing messages. Server no longer allows use of their SMTP server to send messages unless you are connected through a dial-up. When you attempt to send a message through a Simple Mail Transfer Protocol (SMTP) server, you may receive the following error message:

  • The message could not be sent because it rejected you as the sender. Server response ‘550’, Access Denied 0x800CCC78
  • The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was ‘ user@google.com‘. Subject ‘Re: test’, Account: ‘mail.isot.com’, Server: ‘mail.isot.com’, Protocol: SMTP, Server Response: ‘550 5.7.1 Unable to relay foruser@google.com‘, Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79Outlook Server Response 550 Access Denied 0x800CCC78
Follow below resolution steps to fix the issues. Try sending emails after completing each steps to know if issue is fixed.
  • Make sure that your Outlook email account settings are correct.
  • Disable or Uninstall Anti-Virus Software.
  • Create New Outlook Profile and Reconfigure email client.
  • Create New User Account and reconfigure email.

How to Fix Outlook Message Could Not Be Sent Server Response 550 Access Denied 0x800CCC78

Quick Note: Before making any changes in your computer, I suggest you to create a System Restore point  so that you can restore back your computer to previous working stat if something goes wrong.

Step 1: Make sure that your Outlook email account settings are correct.

  • Click on the “Account Settings” under the “Tools” menu.Outlook Server Response 550 Access Denied 0x800CCC78
  • Click on the “Email” and make a double click on the email address by which you are not able to send emails. Outlook Server Response 550 Access Denied 0x800CCC78
  • Through double click other pop-up window will appear, now click on “More Settings buttons. Outlook Server Response 550 Access Denied 0x800CCC78
  • Go to the Outgoing Server tab and select the “My outgoing server (SMTP) requires authentication” checkbox.

Outlook Server Response 550 Access Denied 0x800CCC78

Quick Note : We recommend that you contact your Internet service provider (ISP) for information about the exact incoming and outgoing mail server names and settings that you should use when you configure your Internet email account in Outlook.

Step 2: Disable or uninstall anti-virus.

Check your antivirus manufacturer’s website for additional suggestions or Disable the antivirus software. And Disable the firewall in router. If you found outlook is working fine after disable the antivirus software, recommend you to uninstall the same using their removal tool and reinstall it.

List of manual antivirus uninstallers:

Click the link associated with the antivirus software currently installed on your system and follow the prompts or instructions on the website. After uninstall, reboot the computer.

Refer below links to disable, uninstall or reinstall antivirus software on your computer

Step 3: Create New Outlook Profile and Reconfigure email client.

  • Go to Control panel, Click on Mail Option.
  • Click Show Profiles
  • Click Add
  • Type a name for your profile.
  • Outlook 2007 and above versions support “AutoDiscovery“. This will set up your email account automatically. Enter your name, email address and password and Outlook will try to set up the profile. If it does not work, proceed with “Manually configure server settings or additional server types” and continue.
Refer below links to create Outlook Profile and Mail Configuration.

Step 4: Create New User Account and Configure email.

There is a possibility damaged user account can cause the issues. You can create new user account to make sure user account is not causing the issues.

Conclusion:

Hope above resolutions steps helped you to fix Outlook Message Could Not Be Sent Server Response 550 Access Denied 0x800CCC78 issues. If not you need to contact your email providers or Internet service provider. Meanwhile ask your queries in comments or Forum.