Among my confused thoughts are the following questions: What were the
steps that led to a mail address and mail server in my hotel room? Which
part of the hotel's policy forced me into that? Does any hotel actually
do this? In your understanding, which SMTP server is the STMP client on
my laptop talking to in order to send it's mail?
Hotel and travel systems (e.g. T-Mobile in Starbucks) often intercept
port 25 and send the mail out via their own mail server. Presumably
they do this so that they can rate-limit and keep spammers off their
network. In fact some commercial systems for hotels not only
intercept port 25, they take a look at what you are trying to connect
to and create a fake network tailored to your laptop--so you don't
even have to use DHCP.