Should the term digital mail be capitalized in a sentence?

No, "digital mail" should not be capitalized in a sentence unless it's the first word of the sentence or part of a proper noun.

Here's why:

* It's not a proper noun: "Digital mail" is a generic term, not a specific name of a person, place, or thing.

* It's not a title: "Digital mail" is not the title of a specific service or product.

Examples:

* Correct: We use digital mail to send invoices electronically.

* Incorrect: We use Digital Mail to send invoices electronically.

If it were part of a proper noun, like the name of a service, then capitalization would be appropriate:

* Correct: I receive my bank statements through DigitalMailNow.