Mailbox unavailable. The server response was: 5.4.1 Relay Access Denied

Question

I am getting "Mailbox unavailable. The server response was: 5.4.1 Unable to relay for [email protected]" when I try to send the mail using C# code.

Then I tested my smtp server here.

Here when I enter my smtp server, sender and recipient name. I got followoing message:

MAIL FROM: [email protected]

SMTP -> FROM SERVER:

250 2.1.0 Sender OK

RCPT TO: [email protected]

SMTP -> FROM SERVER:

550 5.4.1 Relay Access Denied

SMTP -> ERROR: RCPT not accepted from server: 550 5.4.1 Relay Access Denied

Message sending failed.

Solution

That's a config issue in the mail servier. It doesn't allow you (your IP, your sender address) to send mail to the recipient.

A properly configured mail server is extremely restrictive with relaying, to prevent it from being abused by spammers to send mails.

Comments

[stephen ebichondo]

The Admin needs to configure the IP on the SMTP Server to allow for mails to be relayed from it

[Ak777]

so, @Anders Abel, its not a config issue in the mail server, but can we say, its a restriction imposed on the mail server? I mean, if they intend to have no other users use any other tools or smtp to send email via this email server but only by specific user account/service-accounts?

[pnmhtkr]

how to configure the IP on the SMTP Server to allow for mails to be relayed from it ?