Praise be to Allaah.
If a proper nikaah (marriage contract) has been done, then you can talk to her however you want, whenever you want, because she is legally your wife, even if you have not yet consummated the marriage. But if the Islamic contract has not yet been done, then she is still a "stranger" (non-mahram) to you, so avoid speaking directly to her. As for corresponding with her via e-mail or the Internet, there is nothing wrong with doing so, as long as the content of your letters is restricted to permissible matters such as advising, teaching and so on. But be very careful not to get dragged into romantic talk or anything else that could inflame desires or result in something bad.
May Allaah help us and you to obey Him and to avoid everything that may earn His wrath. May Allaah bless our Prophet Muhammad.