Email Servers - most recent to oldest updated
Information and howtos about email servers such as Postfix, Dovecot, Maildrop, Sendmail
Email was the first "killer app" of the early Internet and today millions of emails are sent every day using a variety of emails servers such as postfix and sendmail. This section looks at how to use and configure email servers for sending and receiving email, mail filtering with services such as maildrop and procmail, and POP and IMAP servers such as Courier IMAP and Dovecot.
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logwatch "postdrop Illegal seek" and "sendmail queue file write error"
Posted May 4th, 2008 in Email Servers and Linux/Unix/BSD
logwatch is a daily process for reporting and analyzing log files and I recently started getting errors on one of the CentOS Linux machines I manage and no daily report. The particular machine gets thousands of bounced emails per day and the mail log files get very large. logwatch had been reporting to me every single bounced email message so the report emails had got very large before stopping altogether. This post looks at the error messages I got and what I did to fix the problem.
Postfix "file too large" error message
Posted March 14th, 2008 in Email Servers
Running postfix on a CentOS mail server I got the following error message both in a returned email and also in the log file: "cannot update mailbox ... error writing message: File too large". This post looks at the erorr message in the bounce email, the log files, and the solution to the error. This error will also affect postfix mail servers on Red Hat Enterprise Linux and probably other default installs of Postfix as well.
Dovecot "Cannot allocate memory" error
Posted March 12th, 2008 in Email Servers
Installing the Dovecot IMAP/POP server onto a CentOS 5.1 x86_64 machine I was unable to log in via POP or IMAP and got the error message "imap-login: imap-login: error while loading shared libraries: libsepol.so.1: failed to map segment from shared object: Cannot allocate memory" in the mail log file when Dovecot started up. This post looks at the error messages reported and the solution.
Updating Postfix's virtual alias maps
Posted November 18th, 2007 in Email Servers
Postfix allows you to store virtual alias maps in a text file, which tells postfix how to route virtual email addresses to real users on the system. This setting and the file location is determined in the postfix configuration file /etc/postfix/main.cf like so:
virtual_alias_maps = hash:/etc/postfix/virtual
Postfix SMTP Auth Error "no SASL authentication mechanisms"
Posted November 3rd, 2007 in Email Servers
I have been setting up a new mail server recently with Postfix and SMTP Auth, and got the error message "no SASL authentication mechanisms".
Spamassassion connection refused
Posted October 28th, 2007 in Email Servers (Updated October 28th, 2007)
If you get a message like the one following, then you are filtering emails through spamassasin using /usr/bin/spamc but the spamassassin service is not running. connect(AF_INET) to spamd at 127.0.0.1 failed, retrying (#1 of 3): Connection refused.
Dovecot dead but subsys locked error
Posted October 26th, 2007 in Email Servers
When you restart dovecot, if it won't start up again it's likely the process crashed on startup but left the subsys lockfile in place. This prevents dovecot from starting up again. If you run /etc/init.d/dovecot status and get the error message "dovecot dead but subsys locked" then you have this problem.
Configure postfix to accept mail from external connections
Posted October 25th, 2007 in Email Servers
Postfix by default on CentOS 5 and Red Hat Enterprise Linux is configured to only receive mail on the local network interface. This is good if you are not intending your server to run as a mail server but is one additional step to getting your mail server running when setting up Postfix.
Opening port 25 for mail servers with iptables
Posted November 30th, 2003 in Email Servers (Updated October 24th, 2007)
If you cannot connect remotely to sendmail, postfix or other mail servers on port 25 make sure you have the port opened on your firewall. This article deals with opening port 25 with iptables on RedHat Linux.
Installing maildrop on CentOS 5
Posted October 20th, 2007 in Email Servers and Linux/Unix/BSD
I have been in the process of migrating my websites from a couple of dedicated machines to a VPS (Virtual Private Server) which has a fairly minimal base install of CentOS 5 on it. My existing mailserver runs on Gentoo Linux, running Postfix, courier-imap, maildrop, Spamassassin and ClamAV, with the mail accounts and aliases handled by MySQL.
I would have liked to have run only packages available from the CentOS distribution (plus the addons etc) but neither courier-imap nor maildrop are available in the CentOS package trees. Instead I would need to use either cyrus-imapd or dovecot and maildrop was not available at all.
Sendmail Connection Refused on localhost
Posted November 30th, 2003 in Email Servers (Updated March 19th, 2007)
RedHat often misconfigures the /etc/hosts file when setting the system up and sendmail is unable to send messages, leaving log file messages like "Connection refused by localhost.co.nz".
Starting and Stopping Sendmail with FreeBSD
Posted December 17th, 2004 in Email Servers and Linux/Unix/BSD (Updated May 24th, 2005)
Management of sendmail is done on FreeBSD by changing to sendmail's directory (/etc/mail) and running "make" followed by the appropriate command. This either needs to be done as root or using sudo.
Sendmail remote connection refused
Posted November 30th, 2003 in Email Servers (Updated May 24th, 2005)
How to enable sendmail to accept remote connections. By default most distributions (or when compiling sendmail yourself) will only allow local connections for security reasons.
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