SSL support in evolution appears to require that the server also be running the
obsolete smtps (TCP port 465) service -- it can't just negotiate STARTTLS over
TCP port 25 as is now the standard (RFC 2487).
Not sure if this is a bug, a feature request, or something I've misconfigured on
my end ;-). My guess is that it's a feature request....
STARTTLS is on the feature list for the next version of evolution unless I'm
completely misremembering things