This seems like a reasonable desire. My own SMTP actually runs on 587 as well. The attached patch adds two new configuration options under [mail] for "port" and "local_hostname". Since I'm new here I'll make run it by the other devs and then commit it to CVS in the next few days if they don't have any objections or suggestions for improvement.
File Added: 0001-Add-port-and-localhost-params-for-mail.patch