Dictating hyphen or dash over the phone

How should I dictate hyphen in email address or url over the phone ?

My email is gabriel hyphen glenn at gmail dot com

My email is gabriel dash glenn at gmail dot com

The short answer is: it doesn't matter. The listener will probably type the same thing in either case.

But what's the difference between a hyphen and a dash, anyway?

First of all, there are three lengths of what are all more or less dashes: hyphen (-), en dash (–), and em dash (—) ...

The hyphen connects two things that are intimately related, usually words that function together as a single concept or work together as a joint modifier (e.g., tie-in, toll-free call, two-thirds).

The en dash connects things that are related to each other by distance, as in the May–September issue of a magazine; it’s not a May-September issue, because June, July, and August are also ostensibly included in this range...

The em dash has several uses. It allows, in a manner similar to parentheses, an additional thought to be added within a sentence by sort of breaking away from that sentence—as I’ve done here...Em dashes also substitute for something missing. For example, in a bibliographic list, rather than repeating the same author over and over again, three consecutive em dashes (also known as a 3-em dash) stand in for the author’s name. In interrupted speech, one or two em dashes may be used: “I wasn’t trying to imply——”

https://www.chicagomanualofstyle.org/qanda/data/faq/topics/HyphensEnDashesEmDashes/faq0002.html

According to this common definition, the punctuation in an email address would probably be a hyphen, since it's used to connect the related parts of the "local-part" of your address. However, email addresses aren't proper English words, and they use symbols in uncommon ways. If a period is the punctuation mark that denotes the end of a sentence, then the . in firstname.lastname is not a period.

So maybe what we really want to know is what's the name of the symbol in the email address.

According to the Internet Engineering Task Force, the "local-part" of an email address can only contain numbers, Roman letters and these additional characters: !#$%&'*+-/=?^_`{|}~ (RFC 2822)

In ASCII (which is the character set that RFC cares about), that symbol is called "hyphen-minus" (because it's meant to represent a hyphen and a minus sign). So if you wanted to be really careful, you could say, "gabriel hyphen-minus glenn," but since most people don't really know ASCII that well, this isn't advisable.