[paxy]

If you want to send plain text, yes. There is a lot of variation among clients when it comes to formatting and layout however.

But then by those constraints you can also count HTTP or SSH or Telnet or any other protocol at that layer.

[Spivak]

Nobody outside of business and advertising cares how annoying it is to write carefully formatted HTML emails.

For any end user, email is the universal communication mechanism.

[AznHisoka]

Also very few people care how well formatted your html emails are. Give me plaintext anyday.

[paxy]

For text based communication SMS absolutely dwarfs email.

[huhweirdyhat]

In what respect? I don't think i've ever gotten an important SMS outside of personal communications, let alone the 50+ emails I get a day that are considered "important" in some way.

[erikpukinskis]

I think your OP probably meant to constrain the point to messaging. HTTP, telnet, etc aren't really messaging, implying asynchronous delivery, they're socket protocols.

I guess in theory you could leave an HTTP packet for someone to pick up months later, but existing networks would time it out.