opensmtpd @6.8.0p2_3: won't start with default config

[wang-songbo (Songbo Wang)]

The daemon won't start with default config on macOS 11.7.4 (Big Sur).

Starting from command line gives the following message (exit code 1):

$ sudo smtpd -dvf /opt/local/etc/opensmtpd/smtpd.conf.dist
debug: init ssl-tree
debug: init ca-tree
debug: init ssl-tree
debug: using "fs" queue backend
debug: using "ramqueue" scheduler backend
debug: using "ram" stat backend
info: OpenSMTPD 6.8.0p2 starting
debug: init ssl-tree
debug: init ca-tree
debug: init ssl-tree
debug: using "fs" queue backend
debug: using "ramqueue" scheduler backend
debug: using "ram" stat backend
setup_peer: klondike -> control[5239] fd=4
setup_peer: klondike -> pony express[5241] fd=7
setup_proc: klondike done
debug: init ssl-tree
debug: init ca-tree
debug: init ssl-tree
debug: using "fs" queue backend
debug: using "ramqueue" scheduler backend
debug: using "ram" stat backend
setup_peer: lookup -> control[5239] fd=4
setup_peer: lookup -> pony express[5241] fd=7
setup_peer: lookup -> queue[5242] fd=8
setup_done: ca[5238] done
debug: init ssl-tree
debug: init ca-tree
debug: init ssl-tree
debug: using "fs" queue backend
debug: using "ramqueue" scheduler backend
debug: using "ram" stat backend
setup_peer: pony express -> control[5239] fd=4
setup_peer: pony express -> klondike[5238] fd=7
setup_peer: pony express -> lookup[5240] fd=8
debug: ca -> control: pipe closed
debug: ca agent exiting
setup_peer: pony express -> queue[5242] fd=9
debug: init ssl-tree
debug: init ca-tree
debug: init ssl-tree
debug: using "fs" queue backend
debug: using "ramqueue" scheduler backend
debug: using "ram" stat backend
setup_peer: control -> klondike[5238] fd=4
setup_peer: control -> lookup[5240] fd=7
setup_peer: control -> pony express[5241] fd=8
setup_peer: control -> queue[5242] fd=9
setup_peer: control -> scheduler[5243] fd=10
debug: init ssl-tree
debug: init ca-tree
debug: init ssl-tree
debug: using "fs" queue backend
debug: using "ramqueue" scheduler backend
debug: using "ram" stat backend
setup_proc: control done
setup_peer: queue -> control[5239] fd=4
setup_peer: queue -> pony express[5241] fd=7
setup_done: control[5239] done
setup_peer: queue -> lookup[5240] fd=8
setup_peer: queue -> scheduler[5243] fd=9
setup_proc: lookup done
setup_done: lka[5240] done
setup_proc: pony express done
setup_done: pony[5241] done
setup_proc: queue done
setup_done: queue[5242] done
debug: control -> scheduler: pipe closed
debug: rsa_engine_init: using RSA privsep engine
debug: ecdsa_engine_init: using ECDSA privsep engine
debug: control agent exiting
debug: pony -> queue: pipe closed
debug: pony agent exiting
debug: lka -> queue: pipe closed
debug: lookup agent exiting
debug: init ssl-tree
debug: init ca-tree
debug: init ssl-tree
debug: using "fs" queue backend
debug: using "ramqueue" scheduler backend
debug: using "ram" stat backend
setup_peer: scheduler -> control[5239] fd=4
setup_peer: scheduler -> queue[5242] fd=7
setup_proc: scheduler done
debug: bounce warning after 4h
setup_done: scheduler[5243] done
smtpd: setup done
debug: scheduler -> control: pipe closed
debug: queue -> control: pipe closed
debug: scheduler agent exiting
debug: queue agent exiting
debug: parent -> control: pipe closed
smtpd: process control socket closed

[wang-songbo (Songbo Wang)]

Replacing the line in the default config

listen on localhost

by the two lines

listen on 127.0.0.1
listen on ::1

resolves the problem.

I think it is related to the problem reported in ​this GitHub issue.