This is still happening after a reboot, Fedora 28. Restarting dovecot fixes the problem. Does anyone know if it could be related to this bug report? https://bugzilla.redhat.com/show_bug.cgi?id=103401#c130 and suggested work around to add ports to /proc/sys/net/ipv4/ip_local_reserved_ports?

Nov  8 12:21:41 ourdomain dovecot[1386]: Error: service(pop3-login): listen(*, 995) failed: Address already in use
Nov  8 12:21:41 ourdomain dovecot[1386]: Error: service(pop3-login): listen(::, 995) failed: Address already in use
Nov  8 12:21:41 ourdomain dovecot[1386]: Error: service(imap-login): listen(*, 993) failed: Address already in use
Nov  8 12:21:41 ourdomain dovecot[1386]: Error: service(imap-login): listen(::, 993) failed: Address already in use

dovecot --version

2.2.36 (1f10bfa63)

dovecot -n

# 2.2.36 (1f10bfa63): /etc/dovecot/dovecot.conf

# OS: Linux 4.18.16-200.fc28.x86_64 x86_64 Fedora release 28 (Twenty Eight)

# Hostname: ourdomain.com

auth_debug = yes

debug_log_path = /var/log/dovecot-debug.log

mail_debug = yes

mbox_write_locks = fcntl

namespace inbox {

inbox = yes

location =

mailbox Drafts {

special_use = \Drafts

}

mailbox Junk {

special_use = \Junk

}

mailbox Sent {

special_use = \Sent

}

mailbox "Sent Messages" {

special_use = \Sent

}

mailbox Trash {

special_use = \Trash

}

prefix =

}

passdb {

driver = pam

}

ssl = required

ssl_cert = </etc/letsencrypt/live/ourdomain.com/fullchain.pem

ssl_cipher_list = PROFILE=SYSTEM

ssl_key = # hidden, use -P to show it

userdb {

driver = passwd

}

protocol imap {

mail_location = mbox:~/mail:INBOX=/var/mail/%u