It’s not easy — and may not even be possible.
Maybe.
There’s no public directory or phone book you can look at that maintains a list of phone numbers and email addresses.
You’re going to have to do a little legwork and be a lot lucky.
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Getting a phone number from an email address
There’s no direct way to find someone’s phone number from their email address. Respecting privacy is important, and using some means of discovery could even be unethical. Try searching online or on social media or checking public records or online directories, but success is unlikely and sometimes costly. In cases of harassment or illegal activities, contact law enforcement.
Privacy concerns
I have to start by suggesting you respect their wishes. It’s certainly their right not to give you their phone number if they don’t want to. Finding it some other way will likely be considered an invasion of their privacy.
While I won’t be suggesting any illegal approaches, it’s worth understanding that ignoring their wishes may be unethical and unproductive.
There are scenarios where it’s desirable and even necessary, but at least think twice.
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Most email services require their users to provide a phone number. It’s generally for account recovery and to prevent bots from creating massive numbers of accounts. There are some services that don’t, but the most popular do. And, of course, ISP-provided email accounts have the number as part of the internet service they’re providing.
This is considered private, confidential information. You can ask the email provider all you like, but they’re not going to tell you (unless you’re law enforcement, and that’s a whole different scenario).
That’s why I say you have to do some legwork.
Search
Your first reaction might be to head for your local search engine. Sadly, this rarely works. Here’s the problem: even if you search for an exact string by placing it in quotes — such as “leo@askleo.com” — most popular search engines ignore the quotes and treat it as separate tokens. Typically that means the search is for “leo” and “askleo.com”, or even worse, “leo”, “askleo”, and “com”. Not helpful.
Well, not very helpful. It’s worth performing the search in case something useful turns up, but unfortunately, it’s not the search you might think it is.
Social media accounts
One place people often “leak” their information is on social media. Some have an option to “allow people to find me if they know my email address”.
It’s definitely worth a trip to the more popular social media services like Facebook, Twitter, Instagram, TikTok, and others to see if a search turns up anything useful.
You may get lucky and find more information; perhaps even the phone number. Sometimes the additional information can also help refine your search.
Public records
If you know where the person is located, public records are often a source of interesting information. Examples might include tax records, voter registration information, and other information made available by an assortment of public agencies.
Depending on the amount of information you have and the type(s) of records you have access to, you can sometimes find email addresses, phone numbers, physical addresses, and more. Not all jurisdictions make this kind of information available online, and most have privacy protection in place, but it’s another place to potentially gather information in your search.
Online directories
When I search online for someone by name, many of the search results are for online directories. Depending on the uniqueness of the name, they may indicate that they found several people by that name in the area that I’m searching.
The problem? If you want the details, they’ll ask you to pay. Sometimes it’s a little; sometimes it’s more; sometimes it’s a subscription.
And sometimes the promised information is nowhere to be found even after you pay.
I avoid those. Always. Unless you have specific prior experience with one and are willing to pay, I suggest you avoid them as well.
Law enforcement
Honestly, if the reason you’re looking for someone’s phone number is because they’re harassing you or doing something illegal, the right thing to do is to go to law enforcement. They have the tools and the authority to get the information if it rises to the level of having broken the law.
The problem here is that not all law enforcement agencies have the time and resources to devote to things that aren’t truly serious and perhaps life-threatening. And some simply don’t have the expertise.
But it’s definitely worth reporting if you believe the situation qualifies for law-enforcement action.
Do this
My recommendation is that you respect the person’s wishes for privacy unless this is some kind of legal issue, in which case you should involve the authorities.
You can certainly try some of the techniques I’ve outlined above, but I would caution you not to get your hopes up.
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Leo mentioned this in the article, but it was the thing that stood out to me in the question. The questioner said they won’t share their phone number. That should be reason enough to stop trying.