[HECnet] TOPS-20 outgoing mail relay config

Long story short: after moving to the other side of the country a year ago, I finally (recently) had time to get my TOPS-20 system (KLH10) back up and on HECnet. Only to discover that Comcast (cablemodem service), in their wisdom, blocks port 25 in and out, in an effort to "combat spammers". This rather complicates my e-mail setup in TOPS-20. For incoming, I simply created a transport relay on an external mail server that I control in order to deliver mail on an alternate port number that isn't blocked, and then simply port forward it from my firewall to tcp port 25 on the TOPS-20 server. That was the easy part. Outgoing mail from TOPS-20 is proving to be a bit more difficult. I was thinking I may be able to intercept all outgoing traffic from TOPS-20 bound for port 25 at whatever smtp server, and redirect it to a single smart host (mail server on the net which I control), on an alternate port that isn't blocked. Might work. The reason I'm asking about this here, is I'm curious given the mail transports at LEGATO and CHIMPY on HECnet, if anyone has tried simply setting one of them up as a "smarthost" relay for all outgoing mail in TOPS-20, perhaps via the <mail>mailer-relay-info.txt config file. Unfortunately the syntax of mailer-relay-info.txt is a little confusing; despite the explanation in the file's comments, there are no clear examples, and trying to follow the logic of the options in the MMAILR MACRO assembly code is less than helpful in modern mail server context (transmogrify?? who's domain??). Any suggestions welcome. -Mark