Firstly: 

One of the essential aims of Islamic sharee’ah is to protect lineages and honour. For that reason Allaah has forbidden zina (illicit sexual relationships) and has forbidden the means that may lead to that, such as a man being alone with a woman who is not his mahram, sinful looking, travelling without a mahram, a woman going out of her house wearing perfume and makeup, and clothed yet naked. Another of these means is a man talking with a woman and her speaking softly to him and tempting him and provoking his desire, making him fall into her trap, whether that is when they meet in the street or talk on the phone or correspond in writing etc. 

Allaah forbade the wives of His Messenger (peace and blessings of Allaah be upon him) – who were pure women – to display themselves like that of the times of ignorance (Jaahiliyyah) or to speak in soft tones lest those in whose hearts was a disease be moved with desire, and He commanded them to speak in an honourable manner. Allaah said (interpretation of the meaning): 

“O wives of the Prophet! You are not like any other women. If you keep your duty (to Allaah), then be not soft in speech, lest he in whose heart is a disease (of hypocrisy, or evil desire for adultery) should be moved with desire, but speak in an honourable manner”

[al-Ahzaab 33:32] 

See question no. 10221

Conversations and correspondence between men and women on the internet are one of the means of fitnah (temptation) and evil. That is because these conversations could go too far, which in turn often leads to love and infatuation. Hence we must be strict about these matters and keep away from them, seeking the pleasure of Allaah and hoping to avoid His punishment. 

How often have these conversations led people into evil, and made them fall in love and led some of them to something that is even worse than that. See question no. 34841. 

Shaykh Ibn Jibreen was asked: What is the ruling on correspondence between young men and women, knowing that this correspondence is free of any immoral content or love? 

He replied: 

It is not permissible for anyone to correspond with a woman who is not his mahram, because of the fitnah involved in that. The correspondent may think that there is no fitnah, but the Shaytaan will keep on at him until he makes him fall in love with her and her with him. The Prophet (peace and blessings of Allaah be upon him) ordered the one who hears of the Dajjaal to flee far away from him, and he said that a man may come to him as a believer but the Dajjaal will keep on at him until he leads him astray. 

Correspondence of young men with young women involves a great deal of fitnah and danger, and it must be avoided, even if the questioner says that there is no love or desire involved. End quote. 

Fataawa al-Mar’ah, compiled by Muhammad al-Musnad, p. 96. 

Secondly: 

The fasting person is enjoined to fear Allaah and to do what He has commanded, and to avoid what He has forbidden. 

The purpose of fasting is not simply to refrain from eating and drinking, rather the purpose is to attain taqwa or piety – “that you may become Al-Muttaqoon (the pious” [al-Baqarah 2:183] – and to discpilne oneself, and to give up bad deeds. Hence the Prophet (peace and blessings of Allaah be upon him) said: “Fasting is not just giving up food and drink, rather fasting is giving up idle and obscene speech.” Narrated by al-Haakim; classed as saheeh by al-Albaani in Saheeh al-Jaami’, 5376. 

In the answer to question no. 50063 we have explained the effect that sin has on the fast, and that it may take away the reward altogether. 

And Allaah knows best.