When sending email using an email client on your computer such as Outlook, Thunderbird or Mac Mail and you receive the error "550 Access denied - Invalid HELO name", it just means you have not ticked the option "My outgoing server (SMTP) requires authentication" in your email client. For the steps on enabling this feature in common email clients, please see below:
Microsoft Outlook (see image)
- From the Menu Bar, Click Tools then Click E-mail Accounts
- Select "View or change existing e-mail accounts" then Click "Next"
- Select your Email account then Click "Change"
- Click "More settings"
- Select "Outgoing Server" tab
- Select the box beside "My outgoing server (SMTP) requires authentication"
- Select "Use same settings as my incoming email server"
- Click "Ok"
- Click "Next"
- Click "Finish"
Thunderbird
- From the Menu Bar, Click Tools, then Account Settings
- This will bring up the Account Settings window where you can click on Outgoing Server (SMTP) at the bottom of the list in on the left side of the window.
- Back in the middle of the window, select the appropriate outgoing server and click the "Edit" button.
- Make sure "Authentication method" is set to "Normal password"
- Click OK to close the SMTP edit window and again on the Account Settings window.
Mac Mail
- From within Mac Mail Click Mail, Preferences, then Accounts
- Near the bottom of the window, look for Outgoing Mail Server (SMTP), click the drop down arrow and select "Edit SMTP Server List..."
- Click the Advanced button in the middle of the window and make sure Authentication is set to "Password."
- Click OK to close the edit window
