What is the ruling on dealing with online text-based friendship chat programs, without hearing the speaker's voice?

Islam has forbidden the relationship between a man and a woman except through a legitimate marriage. It is not permissible for a man to address a woman, and vice versa, except out of necessity, and this must be within the bounds of propriety and good manners, as Allah Almighty says: (And when you ask [his wives] for something, ask them from behind a partition. That is purer for your hearts and their hearts), and as He Almighty says: (Then do not be soft in speech [to men], lest he in whose heart is disease should covet, but speak with appropriate speech). Caution must be exercised against addressing women through social networking sites on the internet, as this involves following the footsteps of Satan. Any relationship or friendship that is closer and more direct, such as friendship via telephone or direct meeting, is more severely forbidden and poses a greater danger.