CentOS PostFix let's me connect, will not greet - linux

Question

This is the output of PostFix when I connect via telnet:
[root#mail ~]# telnet localhost smtp
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
nothing here
no response
???
^]
telnet> close
Connection closed.
I can try pretending it is responding, etc, it's accepting the connection, but no communication afterwards. I've tried switched ports, reinstalling, etc. At first it works fine, but after it's first restart with Dovecot(I think), it never responds anymore. Same on remote computers.
main.cf:
[root#mail ~]# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
broken_sasl_auth_clients = yes
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
html_directory = no
inet_interfaces = all
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
message_size_limit = 30720000
mydestination = $myhostname, localhost, localhost.localdomain
mydomain = hackmailer.com
myhostname = mail.hackmailer.com
mynetworks = 127.0.0.0/8, 50.131.19.57
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
proxy_read_maps = $local_recipient_maps $mydestination $virtual_alias_maps $virtual_alias_domains $virtual_mailbox_maps $virtual_mailbox_domains $relay_recipient_maps $relay_domains $canonical_maps $sender_canonical_maps $recipient_canonical_maps $relocated_maps $transport_maps $mynetworks $virtual_mailbox_limit_maps
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES
sample_directory = /usr/share/doc/postfix-2.3.3/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_sasl_path = private/auth
smtpd_sasl_type = dovecot
smtpd_tls_cert_file = /etc/pki/dovecot/certs/dovecot.pem
smtpd_tls_key_file = /etc/pki/dovecot/private/dovecot.pem
smtpd_use_tls = yes
unknown_local_recipient_reject_code = 550
virtual_alias_domains =
virtual_alias_maps = proxy:mysql:/etc/postfix/mysql-virtual_forwardings.cf, mysql:/etc/postfix/mysql-virtual_email2email.cf
virtual_gid_maps = static:5000
virtual_mailbox_base = /home/vmail
virtual_mailbox_domains = proxy:mysql:/etc/postfix/mysql-virtual_domains.cf
virtual_mailbox_maps = proxy:mysql:/etc/postfix/mysql-virtual_mailboxes.cf
virtual_transport = dovecot
virtual_uid_maps = static:5000
master.cf
#
# Postfix master process configuration file. For details on the format
# of the file, see the master(5) manual page (command: "man 5 master").
#
# ==========================================================================
# service type private unpriv chroot wakeup maxproc command + args
# (yes) (yes) (yes) (never) (100)
# ==========================================================================
smtp inet n - n - - smtpd
#submission inet n - n - - smtpd
# -o smtpd_enforce_tls=yes
# -o smtpd_sasl_auth_enable=yes
# -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#smtps inet n - n - - smtpd
# -o smtpd_tls_wrappermode=yes
# -o smtpd_sasl_auth_enable=yes
# -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#628 inet n - n - - qmqpd
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
flush unix n - n 1000? 0 flush
proxymap unix - - n - - proxymap
smtp unix - - n - - smtp
# When relaying mail as backup MX, disable fallback_relay to avoid MX loops
relay unix - - n - - smtp
-o fallback_relay=
# -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq unix n - n - - showq
error 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.
#
# Many of the following services use the Postfix pipe(8) delivery
# agent. See the pipe(8) man page for information about ${recipient}
# and other message envelope options.
# ====================================================================
#
# maildrop. See the Postfix MAILDROP_README file for details.
# Also specify in main.cf: maildrop_destination_recipient_limit=1
#
maildrop unix - n n - - pipe
flags=DRhu user=vmail argv=/usr/local/bin/maildrop -d ${recipient}
#
# The Cyrus deliver program has changed incompatibly, multiple times.
#
old-cyrus unix - n n - - pipe
flags=R user=cyrus argv=/usr/lib/cyrus-imapd/deliver -e -m ${extension} ${user}
# Cyrus 2.1.5 (Amos Gouaux)
# Also specify in main.cf: cyrus_destination_recipient_limit=1
cyrus unix - n n - - pipe
user=cyrus argv=/usr/lib/cyrus-imapd/deliver -e -r ${sender} -m ${extension} ${user}
#
# See the Postfix UUCP_README file for configuration details.
#
uucp unix - n n - - pipe
flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
#
# Other external delivery methods.
#
ifmail unix - n n - - pipe
flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
bsmtp unix - n n - - pipe
flags=Fq. user=foo argv=/usr/local/sbin/bsmtp -f $sender $nexthop $recipient
dovecot unix - n n - - pipe
flags=DRhu user=vmail:vmail argv=/usr/libexec/dovecot/deliver -f ${sender} -d ${recipient}
dovecot.conf
[root#mail ~]# dovecot -n
# 1.0.7: /etc/dovecot.conf
log_timestamp: %Y-%m-%d %H:%M:%S
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(pop3): /usr/libexec/dovecot/pop3-login
mail_location: maildir:/home/vmail/%d/%n/Maildir
mail_executable(default): /usr/libexec/dovecot/imap
mail_executable(imap): /usr/libexec/dovecot/imap
mail_executable(pop3): /usr/libexec/dovecot/pop3
mail_plugin_dir(default): /usr/lib/dovecot/imap
mail_plugin_dir(imap): /usr/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/pop3
namespace:
type: private
separator: .
prefix: INBOX.
inbox: yes
auth default:
passdb:
driver: sql
args: /etc/dovecot-sql.conf
userdb:
driver: static
args: uid=5000 gid=5000 home=/home/vmail/%d/%n allow_all_users=yes
socket:
type: listen
client:
path: /var/run/dovecot/auth-client
mode: 432
user: postfix
group: postfix
master:
path: /var/run/dovecot/auth-master
mode: 384
user: vmail
What makes PostFix not greet?

Answer 1

If I remember correctly, postfix (and other MTA's) have begun strictly implementing the SMTP protocol to help thwart email spam.
In this case, it is possible that you're encountering the initial delay during connection. Most spammer software connects and immediately begins push data to send as many emails in as short a time possible... And if the spammer (or you) begins sending data immediately, the MTA will drop the connection. It works quite well. You have to WAIT for the greeting, which could be a moment or so, especially if postfix is trying a DNS lookup of your IP address, that takes a moment too.
The PostFix documentation of this spammer-thwarting whatchamacallit:
PostFix Pregreet Delay
Basically, wait for the 220-xxx Greeting header before typing/sending anything... otherwise PostFix will consider you a Zombie and blacklist you for a while.
Yes, this option can be turned off. I don't recommend that. If you need non-Zombie-Checking for your connections, consider using the WHITELISTED option as described here:
PostFix Permanent White/Black listing (same document, different anchor)