Meaning of stranger

There was the following sentence in a mail.

"Keep in touch. Don't be a stranger."

Don't be a stranger? What does it mean?

For me, a stranger is a kind of weird, odd or suspicious person. So I checked "stranger" in a dictionary.

It was much different.

Example sentences in the dictionary are;

"I'm sorry I'm a stranger around here."
"A passing stranger"
I see. A passerby isn't a weird, odd and suspicious person. Haha.

"You're quite a stranger./Hello, stranger!"
I see, I see!

But when it comes to a stranger, my brain still images a weird, odd and suspicious person. It seems to take much time to change the image of stranger.