Alina Tugend, “The Anxiety of the Unanswered E-mail.” New York Times, April 19, 2013.

OVER the last few weeks, I’ve repeatedly run up against one of the classic frustrations of modern life — sending out e-mails and hearing nothing back.

In this case, it was business-related and the issues were resolved, later rather than sooner. But like everyone else, I’ve also had times when friends seem to inexplicably drop out of sight and my mind races as I pick through our past interactions, wondering if I’ve somehow offended them.

It’s not just e-mails. Unreturned phone calls, texts and messages via social media can be just as irritating. But I’m going to concentrate on e-mails because for most people (teenage sons excepted), they are the most common tool of business and personal communication.

A large part of the problem, said Terri Kurtzberg, an associate professor of management and global business at Rutgers Business School, is that in face-to-face or phone conversations, “it’s clear how long a silence should last before you need to respond,” she said. “There’s no norm with digital communication.”

The nonresponders — the ones who regularly let e-mails slide through the cracks — are at the opposite end of the spectrum from the constant responders. Those are the ones who can barely look up from their smartphones, even while walking or dining, because they are so intent on answering every query.

I’ve written about the problem of expecting instant responses. So this time I’m going to focus on the laggards. I was curious to hear their side of the story, so I sent out the question to friends (via e-mail) and out over some Web sites.

I was somewhat surprised to get so many responses from people who went into quite some detail explaining why they don’t respond to e-mails.

First of all, I’m talking about answering friends or colleagues, not people you don’t know who are trying to sell or pitch something.

Lack of time and too many e-mails are the most common reasons people say they don’t reply (although some of the busiest people I know are the most prompt responders). Checking their e-mails on one device, like a smartphone, making a mental note to reply more in-depth later, and then forgetting, is another. And, of course, there’s always the possibility your e-mail ended up in the junk or spam folder.

But there are more emotional reasons as well. One is fear of commitment or a hesitation to say no. My friend Janine said she would drop the ball when she was invited to something she didn’t want to go to but thought she should.

“I want to say ‘no’, but feel that the right thing is to say ‘yes’, so I am frozen and then I plan on going back to the e-mail to draft a reply, but it gets buried,” she said. “Then I feel even worse for not replying and put it off again. It’s not nice to leave people hanging, but I do.”

Over the last few years, Adam Boettiger, a digital marketing consultant based in Portland, Ore., said, “We’ve seen an increase in the nonresponse rather than just politely declining. You delete it and hope it goes away, just like if someone comes to your door and you pretend you’re not home.”

Notoya Green, of Manhattan, knows both sides. When she worked as a lawyer, “I used to live by my BlackBerry. If people didn’t respond, I thought it was unprofessional and rude.” Now, the mother of 2-year-old triplets, she’s the one no one can get hold of.“If people send me a message that I don’t want to deal with, it’s easier not to respond,” Ms. Green said. “At this stage, there are so many requests from my children, I can’t deal with requests from adults.”

While time is the major factor, it’s not the only one. Like many others, Ms. Green said she may feel uncomfortable turning people down, so she will just ignore the query.

“Recently, a nanny asked me for a job reference,” she said. “I don’t think the nanny deserves the reference. I thought about responding, but didn’t. To me, it’s easier not to say something.”

But even invitations for play dates and other messages she wants to reply to often just drop to the bottom of the pile and go unheeded, until it’s too late.

“People are very angry and frustrated with me,” she said.

We could all adopt the motto that Ellen Dux, a former film executive, said was popular in the film industry: “No response is the new no.”

The only thing is, that’s not always true.

I received a number of replies to my query from people who said they often put aside an e-mail to give a longer, thoughtful reply later, but then waited too long and felt embarrassed to send it.

“Sometimes, I don’t answer because I don’t have time to give the response I think is deserved, so I put it off until later, then forget and the message winds up being that I didn’t care enough to respond, when, in fact, I cared too much,” my friend Faye said.

The trouble is all the assumptions that get loaded on to that nonreply.

“In the United States, we are very uncomfortable with silence,” said Liuba Belkin, an assistant professor of management at Lehigh University. “We interpret it in a very negative way.”

So as we refresh our screens one more time, we expend lots of useless energy searching our memories trying to recall an inadvertent slight that might have caused a friend to give us the cold shoulder. Or wonder if the latest communiqué we sent to a client was too aggressive — or not aggressive enough.

Or we become angrier and angrier.

An unanswered e-mail “leaves an open loop,” Mr. Boettiger said. “We don’t know whether to book the extra seat or table at the restaurant. Something that could have been responded to with a one-sentence e-mail becomes a long-drawn-out affair and feelings are hurt.”

Sometimes, that silence may be deliberate. There is anecdotal evidence — and continuing research — looking into whether delaying a response to an e-mail can be a good tactic to getting more concessions during business negotiations, Professor Belkin said.

Of course, these e-mail issues could often be solved by making a phone call, quaint as that sounds. Carolyn Bodkin, who works in publishing, said “replying to e-mail is like slaying the Hydra. Once you answer one, it often generates a flurry of more e-mails.”

But, she has a rule. “If the issue is not resolved within six e-mails, I pick up the phone.”

Mr. Boettiger said he also called if he had not received a response after about three e-mails. He knows many people dread phone calls because they fear getting caught up in a time-consuming conversation. But, he said, the answer is to learn the trick of getting off the phone without being rude.

And don’t leave voice mail messages unless you’re sure the person you’re calling listens to them.

Mr. Boettiger has also fashioned his own e-mail system to try to ensure he responds to all the e-mails he should. He first replies to everything that will take two minutes or less. If it’s going to take more than two minutes, “I make an appointment with myself by blocking out time on my calendar to answer the e-mail.”

So, here’s my idea. Those of us waiting for replies shouldn’t be so quick to leap to negative conclusions. It’s unlikely your best friend suddenly hates you. Or you’ve alienated a co-worker. Reach out again.

And to those who habitually don’t respond, try sending a quick e-mail just to say you can’t answer now. And if you really mean no, say no. Most of us can handle rejection. We just can’t handle not knowing.

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