Mark Horvit still checks his mailbox at work every day.

As the executive director of Investigative Reporters and Editors, he's not looking for tips anymore. But he still checks it. And he knows a lot of journalists don't. Horvit gave up sending invites to speak at IRE's annual conference by mail.

But Saturday's story from The New York Times on Republican presidential candidate Donald Trump's taxes offers a good reminder: check your mail. Times reporter Susanne Craig discovered Trump's tax returns in her mailbox one day during one of her routine checks:

I walked to my mailbox and spotted a manila envelope, postmarked New York, NY, with a return address of The Trump Organization. My heart skipped a beat.

Journalists can't rely on technology for everything, Horvit said. There are many measures journalists can take to try and protect sources, but no form of electronic communication is completely safe.

"I think this story serves as an important reminder, if it was necessary, that the old ways still work," Horvit said.

For some news organizations, snail mail works because it's one of only a few ways to reach sources. At The Marshall Project, a nonprofit focused on criminal justice, reporters correspond with prisoners by mail, said Managing Editor Kirsten Danis.

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The downside, of course, is that it takes much longer. A joint project from The Marshall Project and NPR about doubling prisoners in solitary confinement took a lot of back and forth through the USPS, Danis said.

So you have to be patient.

"It becomes like a six- or seven-month reporting process just to do interviews with the subjects in your story," she said.

Also, be careful not to put in too many questions to overwhelm the letter receiver. Explain upfront who you are, what organizations you're with and what you hope to talk about.

"We try to give people as much information as we can," Danis said, "because we know this is going to be a very slow process."

The Marshall Project has never gotten a blockbuster tip in the mail, but there are still plenty of people who are more comfortable communicating that way, Danis said.

"It’s a less intrusive, more respectful way to talk to people in an age where your inbox gets full of unwanted information and your cell phone rings with calls from spammers," she said.

And for some people, letters can also feel more authentic.

Thomas French, a Pulitzer Prize winner, Poynter writing fellow and professor of practice at The Media School at Indiana University, recommended snail mail to his students who were trying to contact a source who didn't respond to emails.

The source is about his age, he said, and he had a tip for how they might get through.

"...I told the kids that older people often place more weight in communications typed on actual paper and saw an old-fashioned letter as more personable and more respectful than email," French said.

The students were reluctant at first. There was some eye-rolling.

"But they indulged me and mailed Mrs. Potenza a letter, and to their surprise, she granted them several interviews, talking with them extensively about something painful but important."

So, check your inbox.

There's been such a trend focusing on electronic communication and encryption, which are all important, Horvit said, but "none should take the place of remembering people still exist in a physical world."