Strongly depends on relationship...
I do bring this up when mentoring others - whether I'm the boss or it's a peer situation, but it's much easier to bring it up gently, and if you don't have a formal advisory relationship and aren't asked for advice, it may be best to skip. If you hear the guy complaining that people don't respond well to his emails, it's a different story.
If, however, you can't make out what he's writing or effectively do your job with the communication you receive from him --- different story! But I'm guessing that if salutations blended onto content is the only problem, this is not a big one, it's a 5 second hiccup and you move on...
Trick is - there is no standard, and it highly depends on form factor. When someone's writing from a traditional keyboard, they write very differently than if they are using a blackberry with their thumbs - if your company's communication mediums are mixed, you have to accept that format is going to get pretty muddy.
If I addressed it at all, it would be from the point of view of being effective. Is his message clear and easy to read? If yes, then move on. If no, then focus on that whether text format changes would help.