According to
http://java.sun.com/products/javamail/javadocs/com/sun/mail/smtp/package-summary.html, a
method used for JavaMail requires a password:

tr.connect(smtphost, username, password);

I had dutifully included the appropriate password, but today found that my
hosting company had changed the password with no prior notice.  While
testing to see what functionality of the domain they had blithely disabled,
I was surprised to find that JavaMail still worked, even with the defunct
password.

Are there conditions under which the JavaMail ignores the password in the
connect method, or is there something strange going on here?

A few weeks ago I changed the first parameter of the connect method to
"localhost" as a workaround for a glitch in which the server suddenly
started delaying regular email for hours and intermittently not sending
JavaMail at all.  The hosting company suggested using "localhost" as the
first parameter in the connect method as a workaround for the unexplained
flakiness of their servers.  I don't know if this removes the need for a
password.