Thursday, April 21, 2016

SMTP Error 554 5.7.1 You Are Not Allowed to Connect

Most of the users who try to send the emails from the Exchange Server to an external domain user face a common error that prohibits the user to connect and email cannot be delivered. The sender will receive a non-delivery Receipt with following SMTP error:
554 5.7.1: You are not allowed to connect
This error will be encountered while sending emails to some specific email addresses. The user gets the delivery failure message i.e. 554 5.7.1. It is a rejection from the recipient domain, as SMTP Code 554 5.7.1 means ‘Not allowed’. The blog will be discussing in depth about the same SMTP Error along with its causes and the possible solution to overcome the error.

Introduction of SMTP Error 554 5.7.1

The error is encountered while users send an email to an external domain but is unable to connect and instead gets a delivery failure error 554 5.7.1. Some of the possible reasons for these types of error are the address in MAIL FROM appears to have insufficient submission rights, is invalid, or is not authorized with the authentication used; the address in a RCPT TO command is inconsistent with the permissions given to the user; the message data is rejected based on the submitting user.

Possible Situations

  • IP has been included in a Real-Time Blacklist maybe because there is Spam coming from your Domain.
  • The Domain/IP has been added to a recipient’s private blacklist.
  • Problems associated with the sender’s reputation, which happens when the spam filter determines that the sender’s IP address has a ‘negative reputation’ and rejects the mail.
  • Issues related with Sender’s DNS that occurs when the receiver’s server checks if the sender has a properly configured hostname, and treat them as a spammer if they do not.
  • Issue occurs when the directory management, a feature of Hosted Email Security (HES) is used that act as an inbound filter using LDAP directories to help prevent spams and recognizes only valid email addresses & domains in organization.

Causes of 554 5.7.1 SMTP Error

The error occurs mainly because of the Sender’s IP or domain added to the blacklist. Some of the causes for an IP to be blacklisted are as follows:
  • Sending an email to list of recipients where the contents of the email suggested it was spam rises the chance of being rejected while sending email from that email address.
  • Sending bulk emails and engaging in email marketing or email newsletter distribution may make the sender become more vulnerable to spam filters increasing chance of being blacklisted.
  • If spam mail is sent automatically from the sender’s email address by hackers or after being infected by virus, it will rise the chance of adding the email address to blacklist.

Common 554 5.7.1 Error Messages

Below are the examples of 554 5.7.1 SMTP Error that occurs when user sends email to sever that could not be connected and failed delivery of email:
  • 554 5.7.1 : Delivery not authorized
  • 554 5.7.1 : You are not allowed to connect
  • 554 5.7.1 : Client host rejected: Access denied
  • 554 5.7.1 : Service unavailable; Client host X.X.X.X blocked
  • 554 5.7.1 : Relay access denied
  • 554 5.7.1 : Recipient address rejected: Access denied
  • 554 5.7.1 : Message cannot be accepted, rules rejection
  • 554 5.7.1 : Message refused by Dictionary check
  • 554 5.7.1 : Relay Access Denied for One Domain
  • 554 5.7.1 : Message cannot be accepted, spam rejection
  • 554 5.7.1 : Message refused by DNSBL check
  • 554 5.7.1 : Sender address rejected: Access denied

How to overcome the SMTP Error 554 5.7.1

Few possible ways to overcome the SMTP Error 554 5.7.1 and to send the email successfully are:
  • Ensure that the ‘FROM’ and ‘RECIPIENT’ addresses are valid and correct
  • Spam Checking software can be installed to protect virus attacks that may send unwanted messages automatically from your email account.
  • Determine the configuration of your SMTP server: specify a DNS signature and make sure that you are logged in and following your mail server’s anti-spam policy.
  • User can check if the email address is not on a blacklist with the help of tools for blacklist check.
  • If the IP has been added to blacklist by mistake, it can be removed using removal form. However, it cannot be removed if it has been added to blacklist more than once.
  • If you are using free email service or does not know how to configure your email server, best solution is to use an SMTP service.
  • SMTP service is a third-party outgoing email server for large-scale email campaigns and does not require additional configuration from end user.
  • Check if your internal network is not compromised by ensuring that the Anti-virus installed in the system is updated regularly.
  • Make sure that the Firewall only allows connections on port 25 for the Anti- Spam or Email Servers.
  • Standard recommendations for SMTP validations should be followed on your DNS records.


The blog has been aimed to describe the issues faced while sending email from the Exchange server to users of external domain. Due to the SMTP Error 554 5.7.1, the users cannot connect to the recipient’s IP or DNS leading to delivery failure of email because of the IP being blacklisted. The blog further discusses about the possible situations that could lead to this error and the ways to overcome the error to help users send the email successfully.


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