THERE MAY BE A FEW holdouts in publishing-world who still require hard-copy queries and manuscripts, but if there are, I have not encountered them. All of the editors and literary agents that I know are fine with receiving their submissions as email attachments; most actually prefer things this way, because digital manuscripts are less of a pain to log, sort, share and store.
Now, I've said before that most newer novelists obsess way too much over the formatting particulars of the manuscript: margin size, line spacing and so forth. Your goal is effortless legibility, and as long as you achieve that, you're golden.
But there is one thing you should give some thought to, and that's what font you are using.
Why? Because not all computers have the same font library. And font usability may vary depending on which particular printer a computer is using as its default.
So even though you may be over the moon about 12-point Myopia Obscuro (no need to Google; I made that one up), unless your recipients have the same font, their computers are going to substitute something else for it, and the substitution might be ghastly. It may even be one of those limited fonts that use plain rectangles as placeholders for things like apostrophes.
And you don't want that.
Now, I know what you're thinking. Adobe PDF was invented just to circumvent this sort of dilemma. But PDF, although acceptable for a one-page attachment, is a bad choice for a multi-page proposal or a manuscript, because it has a longer printer processing time, and you will make no friends at the publishing house if it takes them an hour to print out a single copy of your proposal.
And if what you are sending is the draft of a book that is already under contract, what the publisher wants is a document in a ubiquitous word-processing format: i.e., Microsoft Word.
So if you are sending something to a publisher or an agent, use a font that every computer will have. I use 12-point Times New Roman and recommend you do the same. If you (or the recipient) have a phobia about serifs, then Arial is a good, ubiquitous sans-serif choice.
Even then, things such as line breaks may vary slightly on the receiving end, but the manuscript will arrive looking essentially like what you composed on your screen.
And that's good, because it's your writing that you want to be outstanding. Your typeface shouldn't stand out at all.