Postfix

How to fix "554 5.7.1 Service unavailable; Client host blocked using zen.spamhaus.org; Error: open resolver;" from our server delivery of bounced letters with an error message?

botond published Jan. 2023, 03, 22:11 p.m. time
When conducting electronic correspondence, mail servers strive to filter out unsolicited mail (spam) as efficiently as possible. From time to time it happens that these spam filtering services get blocked by letters that do not contain anything that would justify this. Therefore, it may happen with us that we cannot send an email to a recipient, or that we cannot receive mail from others on our own server. In this description, we will investigate one of the more common server-side "554 5.7.1 Service unavailable; Client host blocked using zen.spamhaus.org; Error: open resolver;" type error.

Postfix

botond published Jan. 2023, 03, 22:05 p.m. time
Postfix is ​​an extremely popular free and open source MTA (Mail Transfer Agent) software developed by Wietse Venema in 1997 and first released in December 1998. Postfix aims to provide a secure and reliable mail service that is resistant to Internet attacks and spam. To this end, Postfix has a number of security features, such as traffic restriction, server and client authentication, virus and spam filtering, and content filtering.

How to fix "dovecot: master: Error: socket() failed: Address family not supported by protocol" errors

botond published 2023/02/25, Sat - 08:03 time
After updating ISPConfig, not all services restarted. In this case, the Dovecot POP3/IMAP mail server and even Postfix threw warnings. Although we fixed these errors earlier, our settings were overwritten again during the ISPConfig update. In this troubleshooter, on the one hand, we fix "Address family not supported by protocol" type errors that cause the service to be inoperable, and we also make their permanent settings so that they remain even after further ISPConfig updates.

How to build and arming our ISPConfig3 server and how to secure our control panel, main services and websites with Let's Encrypt SSL (page 3)

botond published 2023/01/20, p - 23:19 time
With the help of the ISPConfig control panel, we can easily manage the websites on our server, as well as other web services. In this description, we will review how to build and provision our ISPConfig3 server, as well as how to set up free SSL certificates issued by Let's Encrypt for the control panel, main services and our websites. On this page, we check the web services and other components running on the server, then we set up the Let's Encrypt SSL certificates for the control panel and the required services and websites. Finally, we perform a few more fine-tuning tasks and eliminate any problems that may arise.

postfix

The manual page of the postfix Linux command. The postfix command is a program for managing the Postfix mail system.

Perfect server: Debian 10 (Buster) V1.0

botond published March 2020, 01, Thu - 02:17 time
In this tutorial, we build the perfect Debian 10 (Buster) server version 1.0, which we build on the previous Debian 10 (Buster) LAMP server. On this page, we do the following: compression, installation of the mail system, additional settings for MariaDB and Apache, installation of spam filters and anti-virus software.

Perfect server: Debian 9 (stretch) V1.0

botond published 2019. 01. 21., h - 17:40 time
In this tutorial, we build the 9 version of the perfect server for Debian 1.0 (Stretch). The following components will be installed on this page: Postfix, Dovecot, MariaDB, rkhunter, binutils.

Perfect server: Debian 8 (Jessie) V1.0

botond published March 2018, 05, Thu - 03:13 time
In this tutorial, we build the perfect server version of Debian 8, starting with 1.0, with the following major components: Postfix, Dovecot, MySQL, openSSL, rkhunter, Amavisd, SpamAssassin, Clamav. (Page 1)