Edit /etc/my.cnf and locate line that reads as follows
[mysqld]

Make sure line skip-networking is commented (or remove line) and add the following line:
bind-address=[YOUR.SERVER.IP.ADDRESS]

For example, if your MySQL server IP is 10.10.10.1 the config should look like as follows:
[mysqld]
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
language = /usr/share/mysql/English
bind-address = 10.10.10.1
# skip-networking

Also make sure you have access from outside for that user:
GRANT USAGE ON *.* TO '[User1]'@'%' IDENTIFIED BY '[password]';