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454 4.7.1 Relay access denied


Linux SMTP relay – How we protect your mail servers from being open relays

Linux SMTP relay – How we protect your mail servers from being open relays

Protecting mail servers from being used as Linux SMTP open relays, is a major security task we perform as a part of our Dedicated Tech Support services for web hosting providers.

An open mail relay is an SMTP server that allows any host to send mails through it. If it is open relay, users can send mails through that Linux SMTP relay server without authenticating.
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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 <user@domain.com>: 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…)