When I try to use imap_open I get the following error:

Warning: imap_open() [function.imap-open]: Couldn't open stream {mail.domain.com:110/pop3/novalidate-cert/} in /path/to/mailbox.php on line 5
Can't open mailbox {mail.domain.com:110/pop3/novalidate-cert/}: invalid remote specification

My phpinfo says that I have:

IMAP c-Client Version   2007e
SSL Support             enabled
Kerberos Support        enabled

On another server that gives the same phpinfo for imap it works, although that version is 2006. PHP says it was compiled with the following settings:

'./configure' '--disable-path-info-check' '--enable-exif' '--enable-fastcgi' '--enable-ftp' '--enable-gd-native-ttf' '--enable-libxml' '--enable-mbstring' '--enable-pdo=shared' '--enable-soap' '--enable-sockets' '--enable-zip' '--prefix=/usr' '--with-bz2' '--with-curl=/opt/curlssl/' '--with-freetype-dir=/usr' '--with-gd' '--with-gettext' '--with-imap=/opt/php_with_imap_client/' '--with-imap-ssl=/usr' '--with-jpeg-dir=/usr' '--with-kerberos' '--with-libexpat-dir=/usr' '--with-libxml-dir=/opt/xml2' '--with-libxml-dir=/opt/xml2/' '--with-mysql=/usr' '--with-mysql-sock=/var/lib/mysql/mysql.sock' '--with-mysqli=/usr/bin/mysql_config' '--with-openssl=/usr' '--with-openssl-dir=/usr' '--with-pdo-mysql=shared' '--with-pdo-sqlite=shared' '--with-pgsql=/usr' '--with-png-dir=/usr' '--with-sqlite=shared' '--with-ttf' '--with-xpm-dir=/usr' '--with-zlib' '--with-zlib-dir=/usr'