Error: SMTP Error 550

What's Causing This Error

SMTP error 550 usually appears when there is an issue with the authentication of the SMTP client and the SMTP server; in most instances, it means that the authentication is missing. However, there are many other reasons to cause this error; these reasons come with the error code for additional information on the exact cause.

For example:

1. Email error "550 Authentication is required for relay" indicates that the client requires authentication.
2. Server error "550 this domain is not hosted here" indicates that the recipient address is not found or is inaccessible.
3. Server error 550 or 550 Blocked Error indicates that the recipient is blocking your email on the recipient's email server.

Solution - Here's How To Resolve It

To fix these common issues, the user must pay attention to the description that follows the error code. However, the following common causes would require different resolutions.

1. Email error "550 Authentication is required for relay" - The user must check the configuration for proper authentication on the email client.
2. Server error "550 this domain is not hosted here" - The user must ensure that all the recipient email addresses are valid.
3. Server error 550 or 550 Blocked Error - The user may need to check with the recipient to ensure that the sender's email domain or email address is not within a blocklist.