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Emails are one of the most widely used ways of communication nowadays. Especially in the IT industry where everything: starting from meeting schedules ending with contracts concludes, is done mostly via email. Relay Access Denied is a rather common error. It indicates that the server is not letting an email to be sent to another mail server. The most common reasons for this error are:

  • The sender did not authenticate to the outgoing mail server due to some misconfigurations
  • The recipient’s server has determined the sender’s server to be a source of spam, or that it had failed security checks

Reasons for getting a relay access denied error

Firstly, let’s take a look at the whole entire process of sending an email. When you send an email, your email client forwards the email to your own mail server. Then your mail server transmits it on Relays to the recipient’s email server. After that, their email server delivers email to the recipient.

sending email receiving email scheme successfully

So there are 2 servers (aka MX) that are involved – Sender’s MX and Recipient’s MX. If one of these servers rejects the mail, then the sender will see the Relay Access Denied error.

Case 1 – Sender’s MX rejects the email

Before the actual sending of the email, MX of the sender asks to provide a username and password to send emails. If your MX won’t be able to successfully authenticate you before sending the email, then it will deny the email from being relayed on to the recipient’s MX.

Why does it happen? Such precaution is done to keep the spammers out, so they aren’t able to send mail using your server without proper credentials. Sometimes it happens even with trustworthy email users if they forget to turn on auth in their mail clients.

sending email receiving email scheme sender's mx error

Case 2 – Recipient’s MX rejects the mail

If the email was successfully sent from Sender’s MX, then the issue might appear with the recipient’s MX. It will accept a mail only if:

  • The Sender’s MX passed all security checks/spam filters
  • Recipient’s MX doesn’t have any misconfigurations

The most common misconfigurations on recipient’s MX are:

  • SMTP authentication settings are disabled
  • Recipient’s email is invalid/inactive/cancelled
  • DNS MX records are pointing to the wrong server
  • MX has some database errors

sending email receiving email scheme recepient's mx error

Solution for Relay Access Denied error on the user side.

First of all, you should ask your email service provider for assistance and verify your email settings with them. You will need to check that you have proper credentials, such as Mail server, Username, and Password. Further, verify whether or not you should use SMTP Authentication, moreover it might be that you need to use POP before SMTP you should also consider this point verifying settings with your email provider.

So, if it turns out that you are using POP before SMTP then you can run into occasional problems with mobile devices. This is caused by your data network changing due to reduced coverage, either if you’re switching different WiFi hotspots. In such case, your IP address may be changing, in the result, you will send email from a new IP address instead of the IP address you first authenticated with. To counter this issue, try and switch to SMTP Authentication thus you will be able to test if your email provider has enabled this feature as well. If it fails, then you should reach your email provider and request them to enable SMTP Authentication on the mail server.

And lastly, there is always a possibility of spam filters coming into action on the recipient’s server. If it so, then you should ask your email provider to look through the mail servers log files and acquire more information from them regarding how to stop this issue.

Solution for Relay Access Denied error on the mail server side

There are two most common situations why a server owner may face with a such or similar error.

  • First one, when end user attempted to send an email, they may receive and send this error in a bounce back
  • The second one, a person trying to send an email to a user on your server receives an error and they report it to you

You should find something close to this message in your log files.

Moreover, pay attention to the error code. We have noticed a couple of versions for that error:

  • 554 5.7.1 Relay Access Denied – You can see this error code in recipient’s mail server logs when an email is rejected.
  • 454 4.7.1 Relay Access Denied – This error code is observed inside server logs when the recipient server is temporarily incapable to receive emails. In such a case, another attempt to send mail will take place later.

Case 1 – User authentication fail

If all your end users began to receive such an error, then it’s most likely this case. You should review the server authentication configurations. For example, if you are using a Postfix server, you must ensure that SMTP authentication is enabled. To do this, check the configuration file and make sure that the “smtpd_recipient_restrictions” is configured as follows:

smtpd_recipient_restrictions = permit_sasl_authenticated

From time to time when it comes updating server software, there is a possibility that it can change configurations. Therefore, if your mail server was running smoothly all the time, and then it suddenly stops, most likely the reason is the latest software update. For example, cPanel control panel automatically checks for updates during night time. Sometimes new and fresh updates that have been just rolled out may break all things. In such a situation, you can either wait for a new update, or you’ll have to manually change some settings.

If you have used to update your server manually, you should consider having a test server setup similar to your live server. Utilization of such test server for checking updates on it first – is a good practice. Next, if everything works fine on your test environment, you can proceed and roll it out to your live environment.

Case 2 – Authentication database is corrupted

On servers similar to Plesk usernames, passwords, and authenticated IP addresses are stored in the database. Like any other database, this can become corrupted for numerous reasons. But you can always rely on a simple command line to restore a table.

mysqlcheck -r psa smtp_poplocks -uadmin -p

This command will perform the check of the table called “smtp_poplocks” and fix it if it turns out that it’s broken.

Case 3 – External mail server failed anti-spam check on your server

Such a situation may occur when someone is sending email to your end users and sender’s emails may be rejected by spam filters configured on your mail server. In this case, you’ll probably find such entries in your mail logs:

This happens due to Sender Verification Callout or simply Sender Verify spam rule. And it indicates that examplesrv.com rejected an email from sendersrv.com based on this rule.

There are three possible ways to resolve such an issue:

  • You should investigate mail logs. If this happens with trustworthy mailbox and emails from this address are blocked due to anti-spam check too often. Then it’s better to consider updating and disabling that anti-spam rule.
  • If you are sure that server which is sending the email is totally trustworthy, you can simply whitelist this server. But use this with caution, because this will allow all emails from that server pass through without any anti-spam checks. So, if by any chance the whitelisted server will be hacked and used to sent spam, then all that spam will pass through your server.
  • Reach owner of the sending email server, and request him to re-configure his server in such a way to be compliant to your anti-spam rules and checks.

Every mail server should have anti-spam checks enabled. But, you should also consider that if you’ll be too offensive with those checks. Then some of your customers may loss important emails. So, we suggest sticking to the IETF | RFC’s compliant spam checks, which are a reference for most server owners and users.

Case 4 – Anti-spam rules on the recipient server are bouncing back your user’s emails

If it happens that your end users are sending emails and in response, they are receiving them back with such an error code:

  • 454 4.7.1 : Relay access denied

Most likely that your server is not passing the recipient’s server anti-spam rules and checks. As well as it may get on the firewall blacklist on recipient’s side.

In such a situation you should firstly review the headers of the bounced emails. It should bring you more details and info why the email was rejected. Usually, it’s provoked when your server gets on RBL’s (Real-time Blackhole List). Such sites as MxToolbox and MultiRBL will help you to figure this out and check if your server is located in blacklists. Info that you will get from those sites will tell you about any blacklists that you may be on and usually refer to these RBL’s, so you can request them to delist you from those RBL’s. However, before asking to delist your server you should make sure and resolve the origin of getting blacklisted. For example, if a spammer was detected on your server then you have to remove him before asking to remove your server from the blacklist.

The Author

Pavel Konobeyev

Tags

mail server

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