Introduction
Learn how to resolve a common SMTP 550 "Relay Denied" error. This error often occurs because of incorrect authentication on the SMTP server. Learn more about SMTP authentication procedures and how to resolve this error.
Overview of SMPT error 550
The SMTP error code 550 means that the recipient of this email could not be reached. This code may appear for several reasons, such as a wrong email address.
Error 550 "Forwarding rejected" means that the SMTP server did not recognize you as a legitimate sender. The most common cause of the error is the lack of proper authentication on all SMTP servers. This can happen if:
* The SMTP password was not entered correctly.
* The e-mail client does not use the appropriate protocol (such as SMTP-AUTH) to send e-mails.
* The best way to solve this problem is to use the email client setup procedure, test and configure the appropriate email address settings.
Evaluating the SMTP Authentication Method
For example, some servers require users to log in to SMTP using a username and password, but others ask to connect to POP3 before sending an email.
Then go through the email client installation process and make sure you set the correct SMTP authentication method. Many email clients have the "autodiscover" or even "autodetect" attribute for SMTP installations. This is a trusted way to set up SMTP authentication in the email client, but if the SMTP error still occurs, you may need to manually establish the email client.
Authentication
* No
* Kerberos / GSSAPI
* NTLM
You can confirm which system your SMTP host is using.
This may seem obvious, but if your SMTP server requires a password, make sure you enter the password correctly. For complex passwords, you can enter the password in a text editor such as Notepad, and then copy and paste the password into the email client.
Confirm SMTP port
The normal SMTP port is 25, which is really the default SMTP port used by most email clients. But SMTP services can be configured for different openings and you will need to configure the e-mail client accordingly.
The most common SMTP ports are:
* 25
* 587
* 465
* 2525
If you are sending an email from outside the firewall, you must confirm that the appropriate interface is also available in the firewall to allow traffic flow.
Solve problems with the SSL method This is usually reliable, but if the SMTP error still occurs, you must manually evaluate the SMTP authentication method.
There are many potential SSL and authentication combinations available for SMTP servers. Currently, the most common varieties are:
SSL
* No
* STARTTLS
* SSL / TLS
If an SMTP error occurs when sending email from one location, but not from another, and you use the same email client, The SMTP server can be installed to authorize users from a specific IP address or range of addresses.
For example, if you have a notebook with Outlook configured and you can send emails from home, but not from work, the IP address filtering is the fault.
There may also be a firewall problem.