IN real life POPPY MONTGOMERY,  unlike her “Unforget­table” character, seems to have forgotten ALL about getting married!

The  Aussie beauty, 39, secretly tied the knot in 1992 and, just like a scene out of her last TV series, “Without a Trace,” mysteriously vanished just five days after saying: “I do.”

What’s worse, when her late husband’s family tried to contact her to let her know he had died, they got a nasty legal letter in reply.

According to sources, Poppy wed her now-deceased husband – suburban Atlanta-based schoolteacher Charles Harbin III – 20 years ago so she could stay in the U.S. to pursue a career in show business.

“Poppy really used Charles,” said a family insider. “She wooed and married him and then split. She broke his heart.”

And while Charles went on to wed twice more and have two daughters, sources claim he and Poppy never got divorced or had the marriage annulled.

The two met when Charles was an exchange student in Australia in the late ’80s. Charles’ mother, Cheryl Conradis, of Gainesville, Ga., said Poppy came to visit him in 1992 and immediately moved in.

According to their marriage certificate, Charles and Poppy, whose partial real name is Ema Elizabeth Devereux, were wed on Oct. 22, 1992.

After he was killed in a traffic accident last July, Charles’ family contacted Poppy to let her know of the tragedy. BUT instead of condolences, the family received “a threatening e-mail letter from an attorney.”

Said the insider: “Charles’ family would love Poppy to explain her actions, past and present, but would settle for an ‘I’m sorry for your loss.’

“They feel she’s behaved shamefully.”