I hope your emails have a positive effect on your father inshaAllah. As Eric also said, the best thing you can do is make dua. Duaas call for a lot of faith and patience - they might take time coming to fruition. So one must persevere and not give up if matters don't change as quickly as one wishes. Let this duaa stay on your lips constantly and especially after salah. I personally find that the duaa which is made with sincerity and humility, in pain or tears, is either accepted sooner or your anguish is replaced by peace of heart and mind.


Pray salatul hajat inshaAllah and ask of Allah to grant hidayah to your father. It's a prayer offered for a particular need or purpose. After ablution, offer two voluntary rakahs and then make sincere duaa stating what you want to accomplish and request Allah swt's help in it.


Abu Darda (ra) relates that the Messenger of Allah (PBUH) said, "Whoever performs ablution well and offers two voluntary rakahs and completes them to perfection will be granted by God whatever he prays for, either immediately or in Allah's good time."

SubhanAllah.