Misguided SPAM Filtering techniques

[Owen DeLong <owen () delong com>]

I'm seeing an increasing variety of misguided SPAM blocking  
techniques such
that they are starting to become more and more annoying, and, I'm  
curious as
to what solutions/work-arounds others have deployed, and, if anyone  
has any
ideas on how to get these tactics reduced/stopped?

Here's the primary hinderance.

I use an authenticated TLS-protected mailhost at home for submitting my
email for delivery.  Unfortunately, networks have taken to:

        outright blocking 25 and 587 except to their own servers.
        proxying all 25/587 connections in a manner incompatible with TLS
        proxying all 25/587 connections in a manner incompatible with SMTPAUTH
        blocking TLS startup on 25/587 connections

Primarily, I have run up against this in the following networks:

        SPRINT Cellular network (can no longer send email from my phone)
        Public wireless networks
        Hotel networks
        Other WiFi hotspots
        Some DSL providers networks

I can't imagine that these tactics actually do anything to  
significantly reduce
the amount of spam delivered to the internet, so, I'm curious as to:

        1.      Why are they used?
        2.      How do we convince operators to abandon them?
        3.      How prevalent is this problem, and, is it growing as I perceive?

Owen