Stranger who mistakenly received couple's wedding invite sends them a heartfelt note and a sweet surprise

Cassie Warren, 25, and her fiance Jesse Jones, 23, got their own wedding invite back in the mail along with a note, a gift and some sage marriage advice from a total stranger.

The invite was one of nearly 200 and meant for her aunt and uncle who live in Eugene, Oregon, Warren told ABC News. But because the bride-to-be was rushing to get them sent out by March 8, she accidentally sent it to an old address.

"I did not double check to make sure it was the correct address," she said.

"We got the invitation back in another envelope. On the outside of the envelope, it said 'live long and prosper,'" Warren recalled. And the original invitation was enclosed with a note on the front and $20.

"I wish I knew you -- this is going to be a blast," the person who received their invite wrote back to the couple on the envelope.

"Congratulations -- go have dinner on me. I've been married for 40 years -- it gets better with age," the anonymous sender wrote.

Warren said she was initially caught off guard on March 19 when her fiance brought in the mail with a letter from an unknown sender.

"But after I saw the note I was just surprised and blessed that she would do that for a stranger," she explained. "Jesse was confused at first too -- [he wondered] why someone was sending us money, then I read the message to him, and he was shocked and grateful."

Warren has since written a thank you card to the sender for the sweet surprise, she said, and the invite eventually made it to her aunt and uncle.

The couple got engaged on July 4, 2017, and will tie the knot in Oregon on June 16, surrounded by family and friends.

For now, they've already received their first unofficial gift as a married couple and practiced the perfect thank you note.