Mail Server SMTP Error 550 5.7.1 Unable to Relay

Yesterday I was trying to send mail but mail server popups HTTP error with some special error code like Exchnage Server error Code 550 5.7.1 then I searched and found lots of user were facing this error and other SMTP error so I decided to put a detailed discussion and resolution of the error 550 5.7.1. Let us start from basics of SMTP.

What Is SMTP?

SMTP stands for Simple Mail Transfer Protocol. SMTP is used when email is delivered from an email client, such as Outlook Express, to an email server or when email is delivered from one email server to another. It uses port 25. SMTP is a sender end protocol which is responsible for sending data over the network but some time it create trouble and Respond with SMTP error code like Exchnage Server SMTP error 550 5.7.1. Now let us discuss meaning of Error code separately and after understanding the each error code meaning you are able to resolve the trouble easily.

What is HTTP?

HTTP (stand for Hyper Text Transfer Protocol) is an application protocol that enable a user to send the mail and it is foundation of data communication across the world. Here Hyper is structured text that uses logical links (hyperlink) between nodes containing text.

HTTP protocol is also called request/response protocol in client server computing model that is used in distributed, collaborative, hypermedia information systems to stablish a link between sender and receiver.

SMTP error Code Meaning

HTTP protocol enables user to send mail but some time it return a particular error message with some cryptic codes and restrict to send mail. And also keep one thing in your mind that every reply code is an error some time it's just a result containing detail of mail server or an answer to a command.

Every Mail Server HTTP error code is of three digit and each digit have a particular meaning, first digit shows weather the server has accepted the command, encounter an error or fulfilled an action second and third digit shows further description if any syntactic or connection trouble occurred. Now let us discuss each error code meaning in detail.

The first digit generally tells whether the server accepted the command and if it could handle it. The five possible values are:

• 1 Indicates that the server has accepted the command, but does not yet take action. A confirmation message is required. Currently, this is not used.
• 2 Indicates that the server has completed the task successfully.
• 3 Refers to the server has understood the request, but requires further information to complete it.
• 4 Indicates that the server has encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use such temporary failures to keep untrusted senders at bay.
• 5 Indicates that the server has encountered an error.

The second number gives more information. Its six possible values and their meaning given bellow.

• 0 Shows syntax error has occurred.
• 1 Indicates an informational reply, for example to a HELP request.
• 2 Refers to the connection status.
• 3 and 4 are unspecified.
• 5 Refers to the status of the mail system as a whole and the mail server in particular.

The third digit is even more specific and shows more graduations of the mail transfer status. This leads us to the detailed list of ESMTP server response codes, as laid down in RFC 821 and later extensions.

What is SMTP Error 550 5.7.1?

The SMTP virtual server allows relaying only from authenticated users. This configuration is designed to prevent unauthorized users from using your Exchange server to relay mail. Among all SMTP errors, error 550 5.7.1 is common error it comes when sender mail server is unable to connect to the specified receiver this error comes when receiver does not allow relay by restricting the particular domain.

How to fix the SMTP Error 550 5.7.1 Unable to Relay

Here I am going to give you a manual method that will resolve SMTP mail Server Error 550 5.7.1 just follow the steps given bellow.

1. Start Exchange System manager.
2. Use SMTP virtual server for the purpose of sending mail.
3. 3. In virtual server go to properties >> access >> Relay.
4. Now enable the allow computers which successfully authenticate to relay.
5. 5. Close all tabs which are opened and now your SMTP mail server is able to send the mails and instantaneously you can start your communication.

Conclusion

The Exchange Mail Server Error 550 50.7.1 can also occur due to EDB file corruption. In this case you can manually repair corrupted EDB file by eseutil utility, if it fails and recovery processes does not completed successfully then you can go for an export suggested EDB to PST Converter Which recovers highly corrupted EDB file also.