I'm in IT for a Fortune 100 company. Attorneys can always find
something to sue for, winning is a different subject all together.
Sometimes the cases that seem the most ridiculous get the most
attention and have the biggest impact. Think of the lady who sued
McD's for the hot coffee accident. Digging in deeper an attorney
would find prior to that accident there were over 600 burns resulting
from their coffee, enough to make the case serious. Additionally,
what wasn't reported was the actual amount awards to her was later
significantly reduced.

I think in this instance some kind of intent would need to be
established cause.

Anyway, on the IT side of things, this is normal. It happens to
everybody and every company at some point. Email server hiccup, one
goes down, etc. So if your IP address is static, it really doesn't
matter a whole lot. IP addresses only play a small role in email.
The bigger role is established by the email servers and information
embedded in them. Typically what will ban an IP address is the subnet
it is on. For instance, a lot of major sites and email servers are
hosted at server farms that have been assigned a range of IP
addresses, static or not. If a user in that assigned range spams
heavily it sets off red flags and any business tying into various anti-
spam software products will permanently or temporarily block all email
from a specific subnet.

I've also seen email servers sit on email while sending other messages
fine. I've watch messages sit in queue and not go anywhere for days
while other messages transact without issue.

As far as suing, I doubt it would get far. There's way to many
technical issues that would be more common than malice. My IT
division is one of the top 10 best in the entire world, and one of the
least understood things even by the most highly experienced IT
employee is email. It takes somebody who has written an email
application (I happen to have done such a thing) or somebody who
specializes in that field. Even an IT person who specialized in
managing an email server can be completely in the dark to the actual
details that go on. Now, if you talk to a Unix IT person who runs a
Unix based email server, then you have yourself somebody who
understands email.

You'd need an attorney that specialized in information technology
email transmissions, and they're aren't many especially considering
the above mentioned fact about IT experts. While I'm sure your
attorney is good, he's not as good as ours and I doubt he specializes
in this area. I bet he could argue the facts of a case, know the law,
and win, but when it comes to the painstaking details involved in this
situation there's just not enough evidence to prove much. You could
be stuck dead in the water when the information that needs to be
provided by whoever administers the servers has been tainted due to
lack of knowledge.

My opinion is, it was just a normal glitch, check the logs people
posted above otherwise and search for companies that block email.
Consider my Fortune 100 email address has been blocked before and we
couldn't do anything about it due to it being a normal error, I think
you'll be in the same boat.