Switching Fedora 20 sendmail from port 25 to port 587

My fedora server sends outgoing email to smtp.comcast.net.  I've always been able to configure that with just this in /etc/mail/sendmail.mc:

define(`SMART_HOST', `smtp.comcast.net')dnl

But two days ago Comcast finally started blocking port 25 on me (http://customer.comcast.com/help-and-support/internet/email-client-programs-with-xfinity-email/).

There are quite a few posts and articles about switching to port 587.  Below is what I found worked on my Fedora 20 server.

Step 1.  New /etc/mail/sendmail.mc config setup:

define(`SMART_HOST', `smtp.comcast.net')dnl

define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl

define(`ESMTP_MAILER_ARGS', `TCP $h 587')dnl

FEATURE(authinfo)dnl

Step 2. Setup authinfo

Assuming your comcast account is walrushose@comcast.net with password door123 ...

# touch /etc/mail/authinfo && chmod 600 /etc/mail/authinfo

# echo 'AuthInfo:smtp.comcast.net "U:walrushose" "P:door123" "M:PLAIN"' > /etc/mail/authinfo

# makemap hash /etc/mail/authinfo < /etc/mail/authinfo

# chmod 600 /etc/mail/authinfo.db

Step 3. Remake and restart sendmail

# make -C /etc/mail

# systemctl restart sendmail.service

Now my server is happily using port 587 for outgoing email.