Delivery temporarily suspended: Host or domain name not found

Question

I have two independent domain ad.vz and ad2.vz, there is gateway between them. There are 3 postfix servers:

• mailad.ad.vz - postfix server in first domain
• mailsh - gateway with postfix and two network adapters
• mailinet.ad2.vz - postfix server in second domain

Mailsh can connect at once only with one network area. There work relay, which turn up/down eth every 30 second. I start stress test in mailad whitch send 20 letters, 500KB every 30 second. Sometimes queue begins to accumulate. I can see in maillog follow message:

Sep  4 08:51:01 mailsh postfix/error[9602]: CFA5E131A7: to=<[email protected]>, relay=none, delay=33, delays=32/0/0/0, dsn=4.4.3, status=deferred (delivery temporarily suspended: Host or domain name not found. Name service error for name=mailinet.ad.vz type=MX: Host not found, try again)"

Every time when adapter turn up, I send command postqueue -f

Why queue can accumulate ?

mailad postconf:

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
debug_peer_level = 2
html_directory = no
inet_interfaces = all
inet_protocols = all
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mydomain = vzavod.ru
myhostname = mailad.vzavod.ru
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
sample_directory = /usr/share/doc/postfix-2.6.6/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
transport_maps = hash:/etc/postfix/transport
unknown_local_recipient_reject_code = 550
transport settings:
vzavod.ru   local
*       smtp:mailsh.ad.vz

mailsh postconf:

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
debug_peer_level = 2
html_directory = no
inet_interfaces = all
inet_protocols = all
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mydomain = vzavod.ru
myhostname = mailsh.vzavod.ru
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
sample_directory = /usr/share/doc/postfix-2.6.6/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
transport_maps = hash:/etc/postfix/transport
unknown_local_recipient_reject_code = 550

transport settings:

*       smtp:mailinet.ad.vz
vzavod.ru   smtp:mailad.ad.vz

Solution

Looks like your situation looks similar to scenario in this article: postfix in dialup machine.

Taken from that article, here some consideration.

• Disable spontaneous SMTP mail delivery (if using on-demand dialup IP only).

  With below parameter, postfix won't attempt to send email unless you run postqueue -f manually. Place this parameter in main.cf. More info in here.

    defer_transports = smtp # (Only for on-demand dialup IP hosts)
  

• Disable SMTP client DNS lookups (dialup LAN only).

  Disable DNS lookups in the Postfix SMTP and LMTP clients. When disabled, hosts are looked up with the getaddrinfo() system library routine which normally also looks in /etc/hosts. So, place the entry of mailad.ad.vz on /etc/hosts. For example

    # echo "192.168.1.99  mailad.ad.vz" >> /etc/hosts
  

  And add this parameter in main.cf

    disable_dns_lookups = yes #(Only for on-demand dialup IP hosts)
  

Comments

[89c3b1b8-b1ae-11e6-b842-48d705]

" Name service error for name=mailinet.ad.vz type=MX: Host not found, try again)" can you 'see' that host from the server?

[Ladadadada]

Does "There work relay, which turn up/down eth every 30 second." mean that sometimes the server in question is not connected to the network? Or maybe switches networks with a brief downtime between? The default minimal_backoff_time is 300 seconds so if a mail fails to send it won't re-attempt to send for five minutes.

[Kirill]

Ladadadada: If users send e-mails to vzavod.ru ([email protected], for example) they will get it without delay inside windows domain ad.vz. If users send E-mail outside ([email protected], for example) first it come to gateway mailsh.ad.vz, when it become available. Mailsh send command postqueue -f to flush queue from mailad. After 30 second mailsh switch network to another windows domain ad.vz with Internet availability and flush all mails to another postfix server mailinet. So networks have a brief downtime. Problem is sometimes letters can't flush from deferred queue

[Kirill]

tristan: Yes, i can see that host