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How to fix error “454 4.7.1 Relay access denied” in Postfix mail servers

How to fix error “454 4.7.1 Relay access denied” in Postfix mail servers

454 4.7.1 <>: Relay access denied

This is a commonly seen email failure error by web hosts, website owners and server owners who run Postfix mail server. 454 error usually happens while sending to and receiving from external domains.

In our role as Hosting Support Engineers for web hosting companies, we handle many such mail errors and fix them. Here, we’ll see what causes “454 4.7.1 Relay access denied” error and how we fix it. (more…)

What causes “Sender verify failed” SMTP mail error, and how to resolve it in Parallels Plesk Postfix servers

SMTP error from remote mail server after RCPT TO:<>:
host []: 550-Verification failed for <>
550-The mail server could not deliver mail to The account ordomain may not exist, they may be blacklisted, or missing the proper dns entries.
550 Sender verify failed

If you are a Parallels Plesk web host, you would recognize this as one of the common errors reported by your customers.

Sender verify failed can be caused by issues ranging from improper file permissions to RFC non-compliance. Engineers at Bobcares help desk support services collect detailed information regarding the error through log analysis and engaging the customer. The following are the few of the common causes for this error. (more…)

Fix “550 Access denied in Parallels Plesk Postfix mail servers

The mail user reports the error:

Task – Sending reported error (0x800CCC78): ‘Cannot send the 
message. Verify the email address in your account properties. The server 
responded: 550 Access denied – Invalid HELO name (See RFC2821

Corresponding entry in Postfix logs say:

2014-09-12 12:19:45 [] rejected MAIL : 
Access denied - Invalid HELO name (See RFC2821

At Bobcares help desk support services, this is a common error we see in Parallels Plesk shared hosting servers. Strict anti-spam rules or lack of SMTP authentication usually cause this error. Given below are a few scenarios we’ve encountered, and the solutions we provided for them. (more…)

The day my Postfix/SASL server refused to deliver mail

I encountered this issue one Saturday afternoon, on which I happened to be working. Being a Saturday, I expected a relatively quiet day at the office. This was why, I was initially surprised when our monitoring software reported that there were more than 3500 mails present in one of our servers (say, mail queue. Within half an hour, the count had increased to approximately 5000 mails. There goes my quiet Saturday. Sigh.

Before proceeding, I would like to point out that all our servers run on CentOS and use Postfix.

Postfix/SASL troubleshooting

Postfix/SASL troubleshooting


Spam and Email Headers (II/II)

Hey, welcome back! I knew you wanted to know more about deciphering email headers. If you haven’t done so already, please do go through the first part of this series. In this part we’ll be looking into email headers in detail and I’ll disclose what information they hold.


Zimbra- Your Open Source Mail Server

Are you in the lookout for a good open source mail server?

Well, then your first stop would be Zimbra.

Zimbra provides open-source server and client software for numerous applications like messaging and collaboration: email, group calendaring, contacts, and web document management and authoring.