Natalie, 39 – who plays Moira Barton in the ITV soap said she felt especially violated because the letter containing images of naked women with her head stuck on was opened by her 70-year-old mother.
David Watson, 74, had also sent similar explicit mock-ups to Coronation Street stars Jennie McAlpine and Kym Marsh.
“The most upsetting bit was that it came to my home. It was unnerving,” Natalie told the Sunday People.
“I was away at the time and my mum opened it and saw it.
“He had superimposed my head on to older, naked women.
“My mum asked: ‘You never did anything like that, did you?’
“I said, ‘Not only are her knockers much bigger, look at the size of her hands. She could have been a goalkeeper!’
“It was distressing for her. It’s not nice to see your daughter like that.”
Natalie, whose character is set to marry Emmerdale bad boy Cain Dingle next month, has had to tighten security at her home in Harrogate, North Yorkshire.
“I have a big dog called Bronson, a cross between a Rottweiler and a Japanese Akita, who’s very protective,” added Natalie.
“If anyone tried to get in I don’t think they’d get back out.”
Watson, of Daventry, Northants, was handed a 12-week suspended sentence in March after he admitted sending indecent images to Natalie, and the two Coronation Street stars.
He said he did it because he was bored and now the offences had strained his 54-year marriage.
His wife was too embarrassed to go to church.
Natalie said: “As well as feeling violated, it’s upsetting that he has a wife.
“It affects people around you and that’s a shame.”