I've done quite a bit of googling on how to reconfigure postfix to work on a different port, but I still can't fond the line(s) people keep talking about in my master.cf. I'm using OS X Mountain Lion, and my ISP blocks traffic both ways on port 25.

people have said to look for a line that says

smtp  inet  n  -  n  -  -  smtpd

I can't find it.

This is (what I believe to be) unmodified

# ==== Begin auto-generated section ========================================
# This section of the master.cf file is auto-generated by the Server Admin
#  Mail backend plugin whenever mails settings are modified.
smtp      inet  n       -       n       -       1       postscreen
smtpd     pass  -       -       n       -       -       smtpd
dnsblog   unix  -       -       n       -       0       dnsblog
tlsproxy  unix  -       -       n       -       0       tlsproxy
submission inet  n       -       n       -       -       smtpd
  -o smtpd_tls_security_level=encrypt
smtp      unix  -       -       n       -       -       smtp
# === End auto-generated section ===========================================
# Modern SMTP clients communicate securely over port 25 using the STARTTLS command.
# Some older clients, such as Outlook 2000 and its predecessors, do not properly
# support this command and instead assume a preconfigured secure connection
# on port 465. This was sometimes called "smtps", but such usage was never
# approved by the IANA and therefore conflicts with another, legitimate assignment.
# For more details about managing secure SMTP connections with postfix, please see:
#   http://www.postfix.org/TLS_README.html
# To read more about configuring secure connections with Outlook 2000, please read:
#   http://support.microsoft.com/default.aspx?scid=kb;en-us;Q307772
# Apple does not support the use of port 465 for this purpose.
# After determining that connecting clients do require this behavior, you may choose
# to manually enable support for these older clients by uncommenting the following
# four lines.
#465        inet  n       -       n       -       -       smtpd
#  -o smtpd_tls_wrappermode=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
#628       inet  n       -       n       -       -       smtp
pickup    fifo  n       -       n       60      1       pickup
cleanup   unix  n       -       n       -       0       cleanup
qmgr      fifo  n       -       n       300     1       qmgr
#qmgr     fifo  n       -       n       300     1       oqmgr
tlsmgr    unix  -       -       n       1000?   1       tlsmgr
rewrite   unix  -       -       n       -       -       trivial-rewrite
bounce    unix  -       -       n       -       0       bounce
defer     unix  -       -       n       -       0       bounce
trace     unix  -       -       n       -       0       bounce
verify    unix  -       -       n       -       1       verify
sacl-cache unix -       -       n       -       1       sacl-cache
flush     unix  n       -       n       1000?   0       flush
proxymap  unix  -       -       n       -       -       proxymap
proxywrite unix -       -       n       -       1       proxymap
# When relaying mail as backup MX, disable fallback_relay to avoid MX loops
relay     unix  -       -       n       -       -       smtp
        -o smtp_fallback_relay=
#       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq     unix  n       -       n       -       -       showq
error     unix  -       -       n       -       -       error
retry     unix  -       -       n       -       -       error
discard   unix  -       -       n       -       -       discard
local     unix  -       n       n       -       -       local
virtual   unix  -       n       n       -       -       virtual
lmtp      unix  -       -       n       -       -       lmtp
anvil     unix  -       -       n       -       1       anvil
scache    unix  -       -       n       -       1       scache
#
# ====================================================================
# Interfaces to non-Postfix software. Be sure to examine the manual
# pages of the non-Postfix software to find out what options it wants.