All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Sending emails which include inappropriate pictures is unlawful and a form of working corruption in the land, because Allah The Almighty Says: " And work not corruption in the land, after it has been set right, and call upon Him in fear, and in hope - surely the mercy of God is near to the virtuous." {Al-a`raf, 56}. This is also spreading corruption in the land since Allah The Almighty Says: "Truly those who love that indecency should be spread, concerning those who believe, theirs will be a painful chastisement in the life of this world and the Hereafter, and God knows, and you do not know." {An-Nur, 19}. Accordingly, a Muslim shouldn`t help in such sin. Rather, he should use wisdom and fair preaching to stop others from committing this sinful act and protect the Muslim nation against such evils. And Allah Knows Best.