is email a communication protocol?

One could argue that any format that free software supports is a free format; the documentation for it being the source code. It is harder to understand than natural language... unless you are a computer! And let us not forget than the relevant pieces of free software code can be reused in another program (possibly with some limitations on its license) or, better, set apart in a library.

> Well said leny2010.

Thanks :)

They are precisely described in RFCs that anybody can freely read:

• https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol#Related_Requests_For_Comments
• https://en.wikipedia.org/wiki/Post_Office_Protocol#Related_requests_for_comments_.28RFCs.29
• https://en.wikipedia.org/wiki/Internet_Message_Access_Protocol#External_links

> Thanks a lot Leny; that really helps.
>
> STMP, POP, and IMAP are free, right? And then there are other
> proprietary alternatives (as you said)?

I'm not sure what the free software community would call them, or what
the definition, if any, of a free standard is. But in industry speak
they're open internationally accepted standards from a reputable
independent body which are not patent encumbered. This is the 'gold
standard' for any sort of standard. Things like ECMA standards are
often argued not to be of this kind.

Internet standards, including email, are in the form of what are
called RFCs (Request for Comments - a name of historical accident) and
are coordinated, managed and approved by the IETF (Internet
Engineering Task Force). Here's the RFC homepage

http://www.ietf.org/rfc.html

Personally I find many of them quite readable and understandable (but
knowing a local University if you're a student or recent graduate
YMMV). In the email ones you'll find things like a definition of spam
and other things which you might not expect in a technical standard.

There aren't really proprietary _alternatives_, because effectively
all global email between arbitrary parties goes over the Internet for
some of the time[*]. It's more that things like Exchange, Notes, and
Groupwise date from before the time the internet protocols became
dominant. Thus they do their own proprietary thing between themselves
and talk internet email protocols to the rest of the world.
E.g. historically Exchange was as is typical of M$ an adopt, modify,
and subvert of part of an open standard. Internally it at least used
to be an X.500 message store. The X.400 suite, which includes X.500
were in vogue at the time.

Similarly uucp (which is in the repo) and Fidonet were originally
designed to transfer their kinds of email (and files) over POTS (Plain
Old Telephone System) acoustic modems in the same era or earlier.
Computers literally phoned each other up. Neither of these has email
protocols like SMTP, POP & IMAP, they're really file transfers over
modem where email files are dumped in the relevant spool location.
Mainframe email of that era worked on the same principle - spool to
spool copies.

My first connection to the Internet was through a uucp connected
machine through email. AIUI you can still get most of the Internet's
content via email from some server or other (e.g. RMS is said to fetch
web pages that way - no nasty Javascript of course, so it's not all
web content). I've even seen a mention of the email anonymizer chain
still being in operation (but send to it via Tor).

* * *

After spell checking I notice I'm still using the old correctness.
The Internet i.e. the global network is a proper noun, there is only
one, and has a capital i. But an internet is any network which uses
internet protocols. Oh my what a dinosaur. :)