All posts by Don Matteo

lebt in der Schweiz, ist System Engineer MCP bei A-Enterprise GmbH. Mitglied des UNBLOG Knowledge Network. Author und Blogger zu den Themen, Tutorials für Linux und Open Source.

How to fetchmail on Debian 11

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fetchmail on Debian with Postfix retrieving and forwarding e-mails

The fetchmail utility can run in daemon mode to repeatedly poll one or more systems at a certain interval, here on a debian system, collecting mail from servers that support all popular mail retrieval services, such as the POP3 and IMAP.

This tutorial show you how to use fetchmail on a Debian 11 (bullseye) with Postfix. The e-mails from external mail service providers are retrieved and forwarded to the recipients to the mailbox server which receives e-mails from the smarthost. No forwarding is required for the mail accounts, but the e-mails can be scanned by the smarthost for viruses and SPAM before they are delivered to the user’s mailbox.

How to install fetchmail on Debian

fetchmail can be deployed from the Debian standard repository.

$ sudo apt install -y fetchmail

Enable daemon mode in/etc/default/fetchmail

# This file will be used to declare some vars for fetchmail
#
# Uncomment the following if you don't want localized log messages
# export LC_ALL=C

# If you want to specify any additional OPTION to the start
# scripts specify them here
# OPTIONS=...

# Declare here if we want to start fetchmail. 'yes' or 'no'
START_DAEMON=yes

Change START_DAEMON from no to yes.

Create fetchmail global recourcen configuration fetchmailrc for operation as a daemon in/etc/fetchmailrc on debian.

Set Daemon 900
set no syslog
set logfile /var/log/fetchmail
Set Postmaster "Postmaster"
set no bouncemail
set no spambounce
set properties ""

poll pop.gmx.net with proto POP3
user 'john@gmx.net' there with password 'M1HXGLKQJ9OZPCA6V34R' is john@foo.org here options fetchall nokeep ssl sslcommonname mail.gmx.net smtphost localhost

fetchmail poll is fetching emails

fetchmail poll line is created for each mail server from which emails are fetched. Every 15 minutes, the external mailbox from john@gmx.net is retrieved from the POP3 server mail.gmx.net and delivered to the user john@foo.org with smtphost via localhost using Postfix to the mailbox server. So that the logging does not end up in /var/log/mail.log, they are logged in /var/log/fetchmail instead

The Common Name (CN) from the certificate, which must be passed with sslcommonname, can be determined using the web browser, or with hit the following command in the Linux shell or from the Windows command prompt.

$ openssl s_client -connect pop.gmail.com:995 | grep "CN="
# with Windows OS
C:\> openssl s_client pop.gmail.com:995 | findstr "CN ="

  On Windows 10/11, OpenSSL must first be provided, the binaries are available at slproweb.com, or you can install the package with hit the command winget install openssl

fetchmail options

fetchmail provides a number of syntactic features to make it easier to read fetchmailrc. While it is possible to provide credentials for a server on a row, common configurations are specified over a number of different lines. fetchmail is insensitive to whitespace unless the argument is between quotation marks.

There are several options for the Poll statement (for example, nofetchall (default), fetchall, keep, or nokeep).The meanings are as follows:

nofetchall: Get only new messages (default).Unless otherwise specified (e.g. fetchall, keep), this means nofetchall.
fetchall: Fetches all messages, whether seen or not.
keep: Does not delete messages on the server.
nokeep: Deletes the read messages from the server.

Set owner fetchmail for the file fetchmailrc on debian.

$ chown fetchmail /etc/fetchmailrc
$ chmod 0600 /etc/fetchmailrc

The fetchmail daemon restarts.

$ systemctl restart fetchmail

The fetchmail conversation to the external server can be checked with the following command.

$ fetchmail -vv -N --ssl -p pop3 -P 995 -ujohn@gmx.net mail.gmx.net

Test the fetchmailrc configuration file.

$ fetchmail -v -a -k -f /etc/fetchmailrc

Check the fetchmail process on our debian server.

$ ps -ef | grep -v grep | Grep Fetchmail

The output may look something like this.

fetchma+ 23566 1 0 2022 ?        00:01:42 fetchmail -vv -d 900 -a -f /etc/fetchmailrc -L /var/log/fetchmail

Logging now takes place in the fetchmail file on the debian.

$ tail -f /var/log/fetchmail

Something like the following is logged in the fetchmail log file.

fetchmail: awakened at Sat 21 Jan 2023 08:55:45 AM CET
fetchmail: 6.3.24 querying pop.gmx.net (protocol POP3) at Sat 21 Jan 2023 08:55:45 AM CET: poll started
fetchmail: Trying to connect to 212.227.17.169/995...connected.
fetchmail: Certificate chain, from root to peer, starting at depth 2:
fetchmail: Issuer Organization: T-Systems Enterprise Services GmbH
fetchmail: Issuer CommonName: T-TeleSec GlobalRoot Class 3
fetchmail: Server certificate:
fetchmail: Subject CommonName: mail.gmx.net
fetchmail: pop.gmx.net key fingerprint: 36:6D:93:38:DE:58:A2:8B:6D:61:F7:76:1F:56:70:BF
fetchmail: SSL/TLS: using protocol TLSv1.2, cipher ECDHE-RSA-AES256-GCM-SHA384, 256/256 secret/processed bits
fetchmail: POP3< +OK POP server ready H migmx106 1MMFyQ-1p2A592gZq-00YABU
fetchmail: POP3> CAPA
fetchmail: POP3< +OK Capability list follows
fetchmail: POP3< TOP
fetchmail: POP3< UIDL
fetchmail: POP3< USER
fetchmail: POP3< SASL PLAIN
fetchmail: POP3< IMPLEMENTATION trinity
fetchmail: POP3< .
fetchmail: POP3> USER john@gmx.net
fetchmail: POP3< +OK password required for user "john@gmx.net"
fetchmail: POP3> PASS *
fetchmail: POP3< +OK mailbox "john@gmx.net" has 0 messages (0 octets) H migmx106
fetchmail: selecting or re-polling default folder
fetchmail: POP3> STAT
fetchmail: POP3< +OK 0 0
fetchmail: No mail for john@gmx.net at pop.gmx.net
fetchmail: POP3> QUIT
fetchmail: POP3< +OK POP server signing off
fetchmail: 6.3.24 querying pop.gmx.net (protocol POP3) at Sat 21 Jan 2023 08:55:45 AM CET: poll completed
fetchmail: New UID list from pop.gmx.net: <empty>
fetchmail: not swapping UID lists, no UIDs seen this query
fetchmail: Query status=1 (NOMAIL)
fetchmail: sleeping at Sat 21 Jan 2023 08:55:45 AM CET for 900 seconds

  The example shows a login sequence in a somewhat shortened form.

The fetchmail man page provides a lot of useful information.

$ man fetchmail

Outlook E-Mail Internet Headers

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How to view E-Mail internet message headers in Outlook

Outlook offers a way to display the source text of the e-mail or the internet (SMTP) headers to clearly identify the origin of the e-mail. The Internet headers can also be used to analyze server delivery and encoding.

If you want to examine the SPAM status in the message header of an e-mail with Outlook, the section “X-Spam-Flag” with the X-Spam-Score value is of interest, you will notice that the X-Spam status is completely missing in the Internet headers, although these are given by Spamassassin.

View Outlook internet message headers

Open the e-mail and go to File -> Properties.

The X-Spam information is simply truncated by Outlook, if you examine the header with another e-mail client, for example using a webmail application, you’ll find the full unfiltered header. However, Outlook takes the X-Spam-Flag classification into account and moves the message to the Junk E-mail folder if it is received with X-Spam-Flag: YES, as long as the default setting in the Junk E-mail options has not been changed.

Track the entire unfiltered Internet Header

X-Spam header truncated snippet in Outlook:

Authentication results: mta-cu121.middle.org;
	dkim=pass (2048-bit key) header.d=outlook.com header.i=@outlook.com header.b="NDq3pzWF"
X-Spam-Flag: NO
X-Spam Score: 0.501
X-Spam Level:
X-Spam Status: No, score=0.501 tagged_above=-999 required=6.2
	tests=[DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1,
	FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, MIME_HTML_MOSTLY=0.1,
	RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001,
	SUBJ_ALL_CAPS=0.5, TVD_SPACE_RATIO=0.001]
	autolearn=no autolearn_force=no
Received: from mta-cu121.middle.org ([127.0.0.1])
	by localhost (mta-cu121.middle.org [127.0.0.1]) (amavisd-new, port 10024)
	with ESMTP id xiFVOnehSqeY for <john@foo.com>;
	Tue, 10 Jan 2023 15:41:15 +0100 (CET)

  we have noticed in outlook that e-mails are filtered upon received for e-mails marked with the X-Spam flag and if the spam e-mail was sent from an office 365 account, usually from sender domain mail.protection.outlook.com

Internet message headers in new Outlook

An email message internet header provides a list of technical details about the message, such as who sent it. The software used to compose it, and the email servers that it passed through on its way to the recipient. Most of the time, only an administrator will need to view internet headers for a message.

Some senders use spoofing to disguise their email address. By checking the header, you can find out if the email address is different than. It appears, and add it to your blocked senders list.

View message headers in new Outlook

Select More actions button (three dot menu) at the top of the message window and select View > View message details.

Find the sender’s address

Scroll down in the Message details until you find the From field.

Highlight the email address enclosed within < > and right-click to Copy.

Use this email address to block the sender.