Shaykh Abdul-Muhsin Al-Abbaad was asked:
Declaring divorce by means of text message or e-mail. Does it occur ? [i.e. does it count]
“Writing, as it is well-known, divorce is divorce if he sends it [to his wife] or he keeps it with him, it [is this form that] occurs. This is because the action which takes the ruling occurs. We know that if a person writes a divorce even if he does not send it to his wife, the divorce occurs. So how about if he sends it by way of the cell phone or other than that?
[Taken from Sharh Sunan Tirmidhi no. 139]
Faisal Ibn Abdul Qaadir Ibn Hassan