What are the limits of the suitor sitting with his fiancée, and is it permissible to exchange words of love over the phone?

The suitor is a stranger to his fiancée, and it is permissible for him to look at her with the intention of marriage, based on the Prophet's (peace and blessings be upon him) saying: "If one of you proposes to a woman, and he is able to look at what would encourage him to marry her, then let him do so." As for sitting alone with her and being in seclusion, it is not permissible, due to the Prophet's (peace and blessings be upon him) prohibition: "No man is alone with a woman but Satan is the third of them." Likewise, it is not permissible to exchange words that arouse desire, due to the potential harms that may result from it, and because it falls under the category of speaking in a soft manner, which is forbidden in His (the Almighty's) saying: "Then do not be soft in speech [to men], lest he in whose heart is disease should covet."