Email Servers

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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View the message header and body for an email in the exim mail queue

Posted in Email Servers -

You've checked to see what's sitting in the exim mail queue, but want to check the email's header and/or body before deleting it from the queue. Use the -Mvh & -Mvb flags to view these.

Discard mail with exim4 using :blackhole:

Posted in Email Servers -

The most obvious way to discard mail to a particular alias with the exim4 mail server is to send it to /dev/null, but unless file_transport is set in the exim configuration it won't work. You can use :blackhole: instead.

Delete messages from the exim mail queue

Posted in Email Servers -

This post shows how to delete a single message from the exim mail queue and also how to remove all of them using the exim command line tools.

Use exim and exiqsumm to show mail queued by domain

Posted in Email Servers -

There are a number of exim commands to see what's in the mail queue etc; sometimes you need to be able to see what's in the queue by domain, to see where hold ups might be.

Test validity of email address from the command line with exim

Posted in Email Servers and Linux/Unix/BSD -

While trying to troubleshoot why email wasn't being delivered to one of my mail aliases on a new server this morning, I discovered a nifty little trick for testing the deliverability of an email address using exim from the command line.

Free POP/110 and IMAP/143 email providers

Posted in Email Servers -

I have compiled a list of email providers here that support POP3 mail access on port 110 and IMAP mail access on 143, and also the big free webmail providers that do not just to round things off. If you know of any other reliable providers please add a comment or email me.

Prevent sender header being added with Exim

Posted in Email Servers -

I changed the mail server on one of my machines from Postfix to Exim a couple of days ago and discovered it adds a "sender" header by default if the "from" header is not the same as the user that sent the email. This results in the "on behalf of" sort of from address in Outlook. This post looks at the setting to prevent the extra sender header from being added.

Show the sendmail mail queue

Posted in Email Servers -

To check what is currently sitting in the sendmail mail queue use the sendmail -bp command or its alias mailq. This post looks at basic usage of this command and the output from viewing the mail queue.

Show the exim mail queue

Posted in Email Servers -

The exim mail server has a number of command line options including being able to see what's currently in the mail queue. Last week I looked at how to flush the exim mail queue and in this post look at how to view the exim mail queue.

Flush the exim mail queue

Posted in Email Servers -

I have the exim mail server running on one of my customer's webservers. Their internal mail server hadn't been accepting mail overnight so they hadn't got a whole bunch of important emails from the webserver and I needed to flush the exim mail queue. A quick read of the exim man page answered my question about how to do this and I thought I'd write a quick post to show how to flush the exim mail queue.

Changing the Postfix maximum email size

Posted in Email Servers -

I've recently had some of my customers emailing me large image attachments and my Postfix mail server has been rejecting them. A quick look at the postfix configuration showed the message size limit was the default so I needed to increase it. This post looks at how to see what the current email message size limit is with Postfix and how to change it.

logwatch "postdrop Illegal seek" and "sendmail queue file write error"

Posted 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 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.

Updating Postfix's virtual alias maps

Posted 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 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 in Email Servers -

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.

Configure postfix to accept mail from external connections

Posted 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.

Starting and Stopping Sendmail with FreeBSD

Posted in Email Servers and Linux/Unix/BSD -

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 Connection Refused on localhost

Posted in Email Servers -

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".

Sendmail remote connection refused

Posted in Email Servers -

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.