5 causes for “SMTP error from remote mail server after RCPT TO” error, and the fixes

Email errors can be really bothersome – they can hit you hard and unexpected, when you attempt to send an urgent mail.

As part of our Outsourced Hosting Support services for web hosting providers, we resolve email errors faced by website owners.

One commonly encountered email error is “SMTP error from remote mail server after RCPT TO”. It shows up when users try to send mails to other email accounts.

What is the error “SMTP error from remote mail server after RCPT TO”?

This error message is a very confusing one, as it can be triggered due to a number of causes. But usually the bounce message that arrives contains the details about the error.

The RCPT command is used to tell the sender mail server, who the recipient of your message is. The error message denotes that the sending mail server faced an error during that command, while trying to send mails.

To know the exact reason for the error, we examine the entire bounce message that the sender receives. And here are some of the major causes we’ve identified.

“SMTP error from remote mail server after RCPT TO” error – Causes & Fixes!

Mail server configuration issue or blacklisting, anything can cause a mail delivery error. We’ll see how to relate to the cause, from the error message we get.

1. Configuration errors

SMTP error from remote mail server after RCPT TO:<user@domain.com>:
host domain.com [xx.xx.xx.xx]: 550-Please turn on SMTP Authentication in your mail client.
550-(host.domain.com) [yy.yy.yy.yy]: __ is not permitted to relay through this server without authentication.


Cause: The authentication errors mostly occur due to mail client or mail form configuration settings. If you try to send mails without proper authentication of your mail account, the mail server throws this error.

The authentication error also occurs when there is any mail server configuration issue – like domain not present in localdomains file or MX record mismatches.

Fix: The mail client settings should be properly configured with mail account details, SMTP server and port number. For PHP mail forms, using SMTP authentication to send out mails can help resolve this error.

To resolve mail server configuration errors, we examine the mail logs, MX records and related configuration files, and fix the discrepancies that are found in them.

2. Domain blacklists

SMTP error from remote mail server after RCPT TO:<user@domain.com>:
host domain.com [xx.xx.xx.xx]: 550-"JunkMail rejected - host.domain.com [yy.yy.yy.yy]: 
___ is in an RBL, see http://www.spamhaus.org/query/bl?ip=________"
SMTP error from remote mail server after RCPT TO:: host host.domain.com [xx.xx.xx.xx]: 
554 5.7.1 Service unavailable; Client host [yy.yy.yy.yy] blocked using zen.spamhaus.org; http://www.spamhaus.org


Cause: RBLs aka blacklists are used by mail servers to prevent inbound spamming. When blacklist providers such as Spamhaus suspect your mail server as a spam origin, they will blacklist your server IP.

Getting blacklisted indicates that your server had a spammer or someone who is sending mass mails. Many times, server owners get to know about it only when users complain about mail errors.

Fix: Once blacklisted, getting de-listed is a time-consuming procedure. Pinpointing the source of spam and fixing it is the most important step. Then you need to request RBL to remove you from the list.

To ensure seamless mail delivery, it is important to avoid getting blacklisted. At Bobcares, we proactively secure the mail server and keep constant vigil on them to avoid all spamming activities that can cause the server to get blacklisted.


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