ForbiddenError

HTTP (not an error, well should forward)\n

Forbidden

You don't have permission to access /squirrelmail on this server.
Apache/2.0.49 (Gentoo/Linux) mod_ssl/2.0.49 OpenSSL/0.9.7d PHP/4.3.4 Server at example.com Port 80

HTTPS (major error)

Same as above but with 443 as the port

It is possible to make a .htaccess file that forces SquirrelMail to go to HTTPS.

You probably have restrictive settings for your web server (which is good), so add a section like this to your httpd.conf file and restart Apache to grant access to the SquirrelMail directory:\n

<Directory "/usr/share/squirrelmail">
    Options None
    Order allow,deny
    allow from all
</Directory>

I just installed Fedora Core 3 (httpd-2.0.52-3, squirrelmail-1.4.4-1.FC3) and got this error. The problem was that index.php wasn't in the list of default directory indexes, so I added it to /etc/httpd/conf/httpd.conf, line 375.

The new line in httpd.conf is:\n

DirectoryIndex index.php index.html index.html.var

The error message in the log file was:\n

Directory index forbidden by rule: /usr/share/squirrelmail/

None of these worked for me because my SquirrelMail server is behind an Apache2 reverse proxy (on Debian Etch). It turned out that the reverse proxy was misconfigured. All the proxy directives I had to set up seemed right, but the problem was finally located in /etc/apache2/mods-enabled/proxy.conf

There is a section like so:\n

<Proxy *>
    AddDefaultCharset off
    Order deny,allow
    Deny from all
    #Allow from .example.com

    # Define the character set for proxied FTP directory listings
    ProxyFtpDirCharset UTF-8
</Proxy>

And that "Deny from all" should be changed to "Allow from all".