Assalamu alaykum!
Men and women are not to correspond or chat or talk useless talk. It should be straight to the point and only what is ABSOLUTELY necessary.
The scholars have even said that chat forums are not permissible.
Allah says:
قَدۡ Ø£ÙŽÙÛ¡Ù„ÙŽØ*ÙŽ Ù±Ù„Û¡Ù…ÙØ¤Û¡Ù…ÙÙ†Ùونَ (١) ٱلَّذÙينَ Ù‡ÙÙ…Û¡ ÙÙÙ‰ صَلَاتÙÛÙÙ…Û¡ Ø®ÙŽÙ€Ù°Ø´ÙØ¹Ùونَ (٢) وَٱلَّذÙينَ Ù‡ÙÙ…Û¡ Ø¹ÙŽÙ†Ù Ù±Ù„Ù„Ù‘ÙŽØºÛ¡ÙˆÙ Ù…ÙØ¹Û¡Ø±ÙضÙونَ
"Successful indeed are the believers. Those who offer their Salât (prayers) with all solemnity and full submissiveness. And those who turn away from Al-Laghw (idle talk, vain speech)." (23:3)
Everyone here says intention intention to excuse themselves for their actions. "we've never met" "we don't talk on the phone" "our intention is not to flirt" etc..
The actions are an indication of one's intention. Intention is not always enough because the idle talk about nonsense can lead to becoming fond of someone of the opposite sex and so on and so forth.
And Allah Most High even allows us to judge.
Allah (swt) says:
ÙˆÙŽÙ…ÙŽÙ† لَّمۡ ÙŠÙŽØ*Û¡ÙƒÙÙ… بÙمَآ أَنزَلَ ٱللَّه٠ÙÙŽØ£ÙوْلَـٰٓٮٕÙÙƒÙŽ Ù‡Ùم٠ٱلۡكَـٰÙÙØ±Ùونَ
"And whosoever does not judge by what Allâh has revealed, such are the Kâfirûn (i.e. disbelievers - of a lesser degree as they do not act on Allâh's Laws)." (5:44)
THUS, we are obligated to judge by the Book of Allah and the Sunnah of His Messenger (saw).