Port 632 sits in the well-known ports range (0-1023), officially assigned by IANA but practically abandoned. It's a reminder of a more optimistic time in Internet history when people thought they could solve the spam problem by asking nicely.
What Port 632 Was Meant For
Port 632 was assigned to BMPP (Bulk Mail Preferences Protocol), a system proposed in 1998 by Troy Rollo of CorVu Pty Ltd.1 The idea was simple: before sending you promotional email, bulk mailers would check your preferences via port 632. If you didn't want their mail, they wouldn't send it.
The protocol would let recipients express preferences about receiving bulk mailings—particularly useful in jurisdictions that required explicit permission for promotional email. Senders would query port 632 to discover if a mailbox was willing to accept their messages.1
It was a protocol built on the assumption that spammers would voluntarily check if you wanted spam before sending it.
Why It Never Happened
The BMPP draft progressed through several versions between June and July 1998, then expired.1 It was never endorsed by the IETF and gained no formal standing in the standards process. The protocol died quietly, a victim of reality: spammers had no incentive to use a system that would let people say no.
While laws like CAN-SPAM (2003) eventually required opt-out mechanisms, they worked through email headers and web links—not through a dedicated protocol on port 632. The problem BMPP tried to solve got addressed in other ways.
What Actually Uses Port 632 Today
Practically nothing.
Some sources mention port 632 being used for Mac OS X RPC-based services like NetInfo, or IBM Application and Transaction Monitoring Network console communication.2 But these are unofficial, undocumented uses—not the official IANA assignment.
The port exists in the registry. It's reserved. But it's a reservation for a protocol that never arrived.
The Well-Known Ports Range
Port 632 falls in the well-known ports range (0-1023), which means it was assigned by IANA and is supposed to be used only for its designated service. These ports are privileged—on Unix-like systems, only root can bind to them.
But being in this prestigious range doesn't mean the port is actually used. Port 632 is proof that official assignments don't guarantee adoption. The Internet is littered with assigned ports for protocols that never took off.
Checking What's On Port 632
To see if anything is actually listening on port 632 on your system:
On Linux/Mac:
On Windows:
Odds are, nothing will be there. Port 632 is almost certainly quiet on your machine.
Why Unassigned-in-Practice Ports Matter
Ports like 632 reveal something important about the Internet: not every assigned number becomes a living protocol. Some ports are allocated to ideas that seemed good at the time but never survived contact with reality.
These ghost ports serve a purpose—they keep the number reserved in case the protocol ever gets revived, and they prevent someone else from squatting on the number. But mostly they're historical markers, breadcrumbs showing paths the Internet considered but didn't take.
Port 632 wanted to make bulk email polite. The Internet went another direction.
Frequently Asked Questions About Port 632
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