MailEnable:550 This mail server requires authentication

You may receive the below error while sending email from MailEnable.

550 This mail server requires authentication (0) when attempting to send via this SMTP (submission) port

This error could be received when MailEnable SMTP service is configured to force all inbound connections to authenticate. Please refer to the following steps to fix this issue.

1. Login to MailEnable MMC.
   
   
2. Navigate to Servers >> LocalHost >> Service and Connectors >> SMTP.
   
   
3. Right-Click on SMTP and select Properties.
   
   
   
   
4. Click on the Inbound tab. >> Port Settings.
   
   
   
   
5. Untick the option Requires connections to authenticate before sending email from SMTP Port (25) and submission Port (587). Hit Ok Button on Both the Dialogue Box.
   
   
   
   
6. Stop and Start the SMTP Service. You can do it by right click on SMTP.
   
   

         Now, you shouldn't face the issue again.