Fix Error: SMTP 451 (Temporary local problem - please try later)

An issue that many server administrators are currently facing is related to a less common SMTP error that occurs when sending an e-mail message.

SMTP 451 (Temporary local problem - please try later)

It's not about hacking or a problem caused by a configuration error. error SMTP 451 occurs especially on operating systems CentOS cu VestaCP installed, and the error log looks like this:

2020-07-03 11:17:11 Tainted filename for search: '/etc/exim/domains/'
2020-07-03 11:17:11 H=( [] F=<[email protected]> temporarily rejected RCPT <[email protected]>: failed to expand "${extract{1}{:}{${lookup{[email protected]$domain}lsearch{/etc/exim/domains/$domain/aliases}}}}": NULL

I don't know if the problem is also for servers that have cPanel, but on VestaCP sure it's a problem. Virtually no user can send emails, even if the connection to the mail server seemed to be fine.
The error occurs as a result of a configuration incompatibilities in the latest EXIM update for CentOS (exim 4.94-1.el7), and so far there is no "fix" to solve this problem. However, there is a very simple solution.

How to fix SMTP 451 error (Temporary local problem - please try later)

Returning to the previous version of EXIM (downgrade) is the most handy solution for mail servers administrators with VestaCP.

1. We authenticate on Linux via SSH and execute the command lines through which we download and install the old version of EXIM.

rpm -Uvh --oldpackage exim-4.93-3.el7.x86_64.rpm


2. Restart "Exim" and be careful that the "clamd" and "spamassassin" services run.

Fix Error: SMTP 451 (Temporary local problem - please try later)

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Passionate about everything that means gadget and IT, I am pleased to write on from 2006 and I love to discover new things about computers and macOS, Linux operating systems, Windows, iOS and Android.

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