### Fetchmail Quickstart (Verbose Fetch)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Execute a fetchmail operation with verbose output, showing the protocol dialogue between fetchmail and the mail server. This is useful for debugging and initial setup.

```bash
# Fetch verbose (show protocol dialogue) — recommended for first-time setup
fetchmail -v --fetchlimit 2
```

--------------------------------

### Install Fetchmail from Source (Autoconf)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Build and install fetchmail using the autoconf/automake build system. Ensure OpenSSL, gettext, and Python 3.7+ are installed. Run the test suite before installation.

```bash
./autogen.sh          # only needed when building from Git
./configure --with-ssl
make
make check            # run the test suite
sudo make install
```

--------------------------------

### Install Fetchmail from Source (Meson)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Build and install fetchmail using the meson build system. This is an alternative to the classic autoconf method. Ensure all build dependencies are met.

```bash
meson setup build --buildtype=release
cd build
Meson compile
Meson test
sudo meson install
```

--------------------------------

### Install Fetchmail Package (Debian/Ubuntu)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Install fetchmail using the system's package manager on Debian or Ubuntu-based systems.

```bash
sudo apt install fetchmail
```

--------------------------------

### Fetchmail Quickstart (One-Shot Fetch)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Perform a one-time mail fetch using fetchmail. This command will read the ~/.fetchmailrc configuration file and poll all configured servers.

```bash
# One-shot fetch using ~/.fetchmailrc
fetchmail
```

--------------------------------

### Verify Fetchmail Installation

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Check the installed fetchmail version and its TLS/SSL library defaults. This command confirms the installation and provides information about the cryptographic library used.

```bash
fetchmail --version
# Output includes: SSL/TLS library info, default CA paths, version string
```

--------------------------------

### Launch fetchmailconf GUI

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Start the fetchmailconf GUI configuration wizard. Requires Python 3.7+ and Tkinter.

```bash
# Launch the GUI configuration wizard (requires Python 3.7+ and Tkinter)
fetchmailconf
```

--------------------------------

### Fetchmail Authentication Methods

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Configuration examples for various authentication schemes supported by fetchmail.

```ini
# ~/.fetchmailrc — Authentication examples

# Default: auto-select strongest method
poll imap.example.org proto IMAP
    user alice password "s3cr3t"
    authenticate any          # default; probes GSSAPI → CRAM-MD5 → password
```

```ini
# CRAM-MD5 challenge-response (avoids sending password in clear)
poll pop.example.org proto POP3
    user alice password "s3cr3t"
    authenticate cram-md5
```

```ini
# GSSAPI / Kerberos 5
poll imap.example.org proto IMAP
    user alice@REALM.EXAMPLE.ORG
    authenticate gssapi
```

```ini
# NTLM for Microsoft Exchange
poll exchange.example.org proto IMAP
    user "DOMAIN\alice" password "s3cr3t"
    authenticate ntlm
```

```ini
# Implicit (IMAP PREAUTH via SSH tunnel — no password needed)
poll mailhost.example.org proto IMAP
    plugin "ssh %h /usr/sbin/imapd"
    authenticate implicit
    sslproto ''               # disable STARTTLS over SSH
    user alice is alice here
```

```ini
# APOP (MD5 challenge — deprecated, avoid on untrusted networks)
poll pop.example.org proto APOP
    user alice password "s3cr3t"
```

--------------------------------

### Install SSL certificates

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Commands to install SSL root CA certificates for fetchmail to use. This involves creating a directory, copying certificate files, and running a script to generate necessary symlinks.

```bash
mkdir /etc/ssl/certs
```

```bash
cp *.pem /etc/ssl/certs/
```

```bash
perl c_rehash
```

--------------------------------

### Fetchmail User Mapping Example

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/website/fetchmail-FAQ.html

Example of mapping a remote user to a local user in fetchmail configuration. Ensure the local user exists and can receive mail.

```fetchmailrc
user 'remoteuser' there with password '*' is 'localuser' here
```

--------------------------------

### Fetchmail Quickstart (Specific Server Fetch)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Fetch mail from a specific POP3 server using command-line arguments to override or supplement the ~/.fetchmailrc configuration. Includes SSL/TLS options.

```bash
# Fetch from a specific POP3 server with explicit credentials
fetchmail -p POP3 -u alice --ssl mail.example.org
```

--------------------------------

### Fetchmail command line execution

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Example of running fetchmail from the command line. This used to work without a .fetchmailrc file in older versions but now requires specific configuration.

```shell
fetchmail -u "itz" -p POP3 -s bolero.rahul.net
```

--------------------------------

### Full cron job example with NOMAIL handling

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

A complete cron job entry that runs fetchmail every 15 minutes and suppresses the 'NOMAIL' error.

```bash
*/15 * * * * fetchmail -s || [ $? -eq 1 ]
```

--------------------------------

### Fetchmail Configuration Example

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/archived-messages/000154.html

This is a sample fetchmailrc configuration. It sets logging to syslog, defines the postmaster, disables bounce mail, and specifies an ID file. The daemon setting is commented out.

```shell
set syslog
set postmaster "[david at dgreaves.com](https://lists.berlios.de/mailman/listinfo/fetchmail-devel)"
set nobouncemail
set properties ""
#set daemon 180
set idfile /var/run/fetchmail.ids
```

--------------------------------

### Sendmail configuration for fetchmail

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Example sendmail configuration directives to ensure compatibility with fetchmail, particularly for relaying and hostname recognition.

```sendmail
Cwlocalhost
```

--------------------------------

### Fetchmail Configuration (Deliver via MDA)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Configure fetchmail to deliver fetched mail using a Mail Delivery Agent (MDA) instead of SMTP. This example uses maildrop. Ensure the MDA path and arguments are correct.

```ini
# ──────────────────────────────────────────────
# Deliver via MDA instead of SMTP
# ──────────────────────────────────────────────
poll mail.example.org proto POP3 uidl
    user alice password "s3cr3t"
    mda "/usr/bin/maildrop -d %T"
    ssl sslproto tls1.2+
```

--------------------------------

### Debug Fetchmail with Full Protocol Trace

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Execute fetchmail with `-vvv --nodetach --nosyslog` to get a full protocol trace, displaying every server command and response. Use `env LC_ALL=C` for consistent output.

```bash
# Step 2: run with full protocol trace (shows every server command/response)
env LC_ALL=C fetchmail -vvv --nodetach --nosyslog
```

--------------------------------

### Fetchmail configuration for SSL/TLS without authentication

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

This configuration example demonstrates using fetchmail with SSL/TLS via the openssl s_client utility. Note that this method does not authenticate the server.

```fetchmailrc
poll MYSERVER port 993 plugin "openssl s_client -connect %h:%p"
        protocol imap username MYUSERNAME password MYPASSWORD
```

--------------------------------

### Fetchmail Multi-Drop Mode for Demon Internet SDPS

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/website/fetchmail-FAQ.html

Example fetchmail configuration for multi-drop mode with Demon Internet's SDPS. This setup handles multiple email addresses within a single POP3 account and requires specifying local domains.

```fetchmailrc
poll pop3.demon.co.uk proto pop3 aka mailstore no dns:
   localdomains xyz.demon.co.uk my-company.co.uk
   user xyz is \*
```

--------------------------------

### Get Backtrace with GDB

Source: https://context7.com/fetchmail/fetchmail/llms.txt

After enabling core dumps, use GDB with the fetchmail executable and the generated core file (`fetchmail.core`) to get a backtrace of the crash.

```bash
# Once core is written, get a backtrace with GDB
gdb ./fetchmail fetchmail.core
# (gdb) backtrace full
# (gdb) quit
```

--------------------------------

### Configure fetchmail with SSL support

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Enable SSL support during fetchmail compilation. This is the default since fetchmail v6.4.0. If OpenSSL is installed in a non-default location, provide the path to the installation directory.

```bash
--with-ssl
```

--------------------------------

### Use Connection Hooks for Dial-up

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Employ connection hooks to establish a PPP connection before polling and hang up afterwards. Ensure pppd is in your PATH.

```fetchmailrc
poll dialup.provider.net proto POP3
    user alice password "s3cr3t"
    preconnect "pppd call myisp"
    postconnect "pppd call hangup"
```

--------------------------------

### Get Server TLS Fingerprint

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Obtain the TLS fingerprint of a server using `openssl s_client` and `openssl x509`. This is useful for certificate pinning.

```bash
# Get TLS fingerprint of the server (use for sslfingerprint pinning)
openssl s_client -connect imap.example.org:993 </dev/null 2>/dev/null \
    | openssl x509 -noout -sha256 -fingerprint
```

--------------------------------

### Build Fetchmail with wolfSSL

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Configure fetchmail to build with the wolfSSL library instead of OpenSSL. This requires specific compilation flags for wolfSSL itself.

```bash
./configure --with-wolfssl
# wolfSSL must have been compiled with:
#   CFLAGS="-DOPENSSL_COMPATIBLE_DEFAULTS -DWOLFSSL_BLIND_PRIVATE_KEY -O" \
#   ./configure --enable-opensslall --enable-harden --enable-context-extra-user-data
```

--------------------------------

### Fetchmail Configuration for Non-RPA

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Example fetchmail configuration for non-RPA (Remote Procedure Access) polling. It specifies the server, protocol, user credentials, and local user mapping.

```fetchmailrc
poll non-rpa.csi.com via "pop.site1.csi.com" with proto POP3 and options no dns
    user "CSERVE_USER" there with password "CSERVE_POP3_PASSWORD"
       is LOCAL_USER here options fetchall stripcr
```

--------------------------------

### Configure fetchmail with GSSAPI support

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Use this option when compiling fetchmail to enable GSSAPI support, typically for Kerberos V authentication. Specify the root directory of your Kerberos V libraries.

```bash
configure --with-gssapi=/usr/krb5
```

--------------------------------

### Update .fetchmailrc for interface option (fetchmail < 2.8)

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

For fetchmail versions prior to 2.8, the 'interface' option was a global 'set' command. This example shows how to convert it to a per-server option.

```shell
set interface = "sl0/10.0.2.15"
```

```shell
interface sl0/10.0.2.15
```

--------------------------------

### SSL/TLS Utility and Testing Commands

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Commands for obtaining server certificate fingerprints and testing TLS connections.

```bash
# Obtain a server's SHA-256 fingerprint for pinning
openssl x509 -in server-cert.pem -noout -sha256 -fingerprint
```

```bash
# Test TLS connection before committing to config
env LC_ALL=C fetchmail -vvv --nodetach --nosyslog \
    --ssl --sslproto tls1.2+ -p IMAP -u alice imap.example.org
```

```bash
# Allow core dumps for crash debugging (passwords may appear — handle with care)
ulimit -Sc unlimited
fetchmail -Nvd0 --nosyslog -vvv
```

--------------------------------

### Fetchmail Configuration (Daemon Mode)

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Configure fetchmail to run as a background daemon, polling mail servers at a specified interval. Includes settings for logging and a postmaster address.

```ini
# ──────────────────────────────────────────────
# Run fetchmail as a daemon every 15 minutes
# ──────────────────────────────────────────────
set daemon 900
set logfile /var/log/fetchmail.log
set postmaster alice
```

--------------------------------

### Fetchmail configuration with SSL certificate path

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Configure fetchmail to use SSL with a specified certificate path for verification. This is useful when dealing with self-signed certificates or custom CA setups.

```fetchmailrc
poll pop3.example.com proto pop3 uidl no dns
  user foobar@example.com password xyzzy is foobar ssl sslcertpath /etc/ssl/certs
```

--------------------------------

### Resource Limits: Message Size and Warnings

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Set a limit for message size (in bytes) and configure warnings for daemon mode. Messages exceeding the limit are handled according to other options.

```ini
poll imap.example.org proto IMAP
    user alice password "s3cr3t" ssl
    limit 1048576
    warnings 3600
```

--------------------------------

### Fetchmail SSL/TLS Configuration

Source: https://context7.com/fetchmail/fetchmail/llms.txt

Configuration snippets for securing mail retrieval connections using SSL/TLS with fetchmail.

```ini
# ~/.fetchmailrc — Implicit TLS (recommended, dedicated SSL ports 993/995)
poll imap.example.org proto IMAP
    user alice password "s3cr3t"
    ssl                       # wrap entire connection in TLS
    sslproto tls1.2+          # require TLSv1.2 or newer (default since 6.5.0)
    sslcertck                 # verify server certificate (default since 6.4.0)
```

```ini
# STARTTLS on standard port (in-band negotiation, no --ssl flag)
poll imap.example.org proto IMAP
    user alice password "s3cr3t"
    sslproto tls1.2+          # triggers STARTTLS; omit 'ssl' keyword
```

```ini
# Pin server certificate by SHA-256 fingerprint (defense against MitM)
poll imap.example.org proto IMAP
    user alice password "s3cr3t"
    ssl sslproto tls1.2+
    sslfingerprint "{SHA256}AA:BB:CC:DD:EE:FF:..."
```

```ini
# Custom CA certificate bundle (e.g. self-signed corporate CA)
poll imap.example.org proto IMAP
    user alice password "s3cr3t"
    ssl sslproto tls1.2+
    sslcertfile /etc/ssl/certs/my-company-ca.pem
```

```ini
# Client certificate authentication
poll imap.example.org proto IMAP
    user alice
    ssl sslproto tls1.2+
    sslcert /home/alice/.ssl/client-cert.pem
    sslkey  /home/alice/.ssl/client-key.pem
    authenticate external      # skip password; identity comes from cert
```

--------------------------------

### Generating Letter-Sized FAQ PDF with HTMLDOC

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/website/fetchmail-FAQ.html

To create a letter-sized PDF of the fetchmail FAQ, install HTMLDOC, edit the fetchmail-FAQ.book file to change the paper size, and then run the make command.

```shell
make fetchmail-FAQ.pdf
```

--------------------------------

### Workaround for c_rehash with Multiple OpenSSL Versions

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Provides a workaround for issues with OpenSSL's c_rehash script when multiple OpenSSL versions are installed. This ensures the correct OpenSSL binary and certificate path are used.

```bash
env PATH=/opt/openssl3.0/bin /opt/openssl3.0/bin/c_rehash /home/hans/certs
```

--------------------------------

### Initialize va_list before vsnprintf

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/website/fetchmail-SA-2008-01.txt

Ensures that the va_list 'args' is properly initialized using VA_START before each call to vsnprintf. This is crucial because vsnprintf modifies the va_list, and it must be reset for subsequent calls.

```c
/*
 * args has to be initialized before every call of vsnprintf(), 
 * because vsnprintf() invokes va_arg macro and thus args is 
 * undefined after the call.
 */
VA_START(args, message);
	n = vsnprintf (partial_message + partial_message_size_used, partial_message_size - partial_message_size_used,
		       message, args);
va_end (args);
```

--------------------------------

### Configure Sendmail for Red Hat Linux 6.x

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/fetchmail-FAQ.html

Enable SMTP service in Red Hat Linux 6.x by setting DAEMON=yes in the sendmail configuration file and restarting the service.

```bash
DAEMON=yes
/sbin/service sendmail restart
```

--------------------------------

### Build Fetchmail with Latest Flex

Source: https://gitlab.com/fetchmail/fetchmail/-/blob/legacy_6x/website/fetchmail-FAQ.html

If fetchmail dumps core with an invalid rc file, especially on older systems, ensure you have the latest version of flex installed. This resolves issues related to archaic lex versions.

```shell
build and install the latest version of [flex](http://flex.sourceforge.net/)
```