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[partially SOLVED] postfix MX backup local delivery
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Frautoincnam
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PostPosted: Sat Apr 17, 2021 7:44 pm    Post subject: [partially SOLVED] postfix MX backup local delivery Reply with quote

Hi,

I have a primary mail server (postfix) working fine for years, named here PRIMARY (smtp.mydomain)

Now, I want to configure a MX backup (postfix) named here SECONDARY (vps1.mydomain) :
1) to receive all mails when PRIMARY is down, then relaying them
AND
2) to send all local mails to PRIMARY
PRIMARY and SECONDARY have same domain (mydomain)

I only modify SECONDARY postfix configuration.
1) is ok (for the moment)
but I can't have 2)
With mydestination = vps1.mydomain, emails are locally delivered.
With mydestination = localhost, I get bounced "loops back to myself"

I tried a lot of configurations, and never get 1) and 2) working.
I don't know what to try else.

Code:
# comm -23 <(postconf -n | sort) <(postconf -d | sort) | anonyme
compatibility_level = 2
debugger_command = PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin ddd $daemon_directory/$process_name $process_id & sleep 5
inet_protocols = ipv4
luser_relay = postmaster
mail_spool_directory = /var/spool/mail
manpage_directory = /usr/share/man
mydestination = localhost
mydomain = mydomain
myhostname = vps1.mydomain
mynetworks_style = host
myorigin = $mydomain
recipient_delimiter = +
relay_domains = pcre:/etc/postfix/mydestinations
relay_recipient_maps = hash:/etc/postfix/relay_recipients
smtpd_recipient_restrictions = permit_mynetworks permit_sasl_authenticated reject_non_fqdn_recipient reject_unknown_recipient_domain reject_unauth_destination reject_unauth_pipelining reject_rbl_client cbl.abuseat.org
smtpd_relay_restrictions = permit_mynetworks,reject_unauth_destination
unverified_sender_reject_code = 550

Code:
# anonyme /etc/postfix/mydestinations
/^vps1$/                   ACCEPT
/^(.*\.)*mydomain$/  ACCEPT
/^localhost\.localdomain$/      ACCEPT
/^localhost$/                   ACCEPT

/etc/postfix/relay_recipients is populated wqith accepted email adresses.

Surely something very simple, but I can't get it for now.


Last edited by Frautoincnam on Sun Apr 18, 2021 4:36 pm; edited 1 time in total
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Frautoincnam
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PostPosted: Sat Apr 17, 2021 10:33 pm    Post subject: Reply with quote

The only solution I found for the moment to solve my problem is those modifications:
Code:
myorigin = $myhostname
luser_relay = postmaster@mydomain
mydestination = localhost.$mydomain, localhost
recipient_canonical_maps = hash:/etc/postfix/recipient_canonical_maps
relay_domains = $mydomain

and recipient_canonical_maps
Code:
@vps1.mydomain  @mydomain

Surely not so clean, but I couldn't find better.
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pa4wdh
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PostPosted: Sun Apr 18, 2021 3:51 pm    Post subject: Reply with quote

I have a very similar setup as you describe.

Quote:

1) to receive all mails when PRIMARY is down, then relaying them

The mail server doesn't know if it's primary or secondary. It is only advertised as such in DNS.
For example:
Code:

mydomain  IN  MX  10 mx1.mydomain
          IN  MX  20 mx2.mydomain

The 10 and 20 here are the priorities. Sending MTA's should try the lowers one first and go to the second one if that fails.

Quote:

2) to send all local mails to PRIMARY

For that i left "mydestination" empty/default, because that would make it try to deliver that mail locally, which is not what you want. What you're searching for might be "relay_domains", where i set all the domains i own and which should be relayed to the primary when it's up&running. I also set relayhost to my primary mail server (in my case connected via a VPN). To make sure you're not an open relay (which will be abused by spammers) i set:
Code:

smtpd_recipient_restrictions = reject_unauth_destination
smtpd_relay_restrictions = permit_auth_destination,reject_unauth_destination

When get a new domain, basically the only thing i have to modify on the backup mailserver is the "relay_domains" line.

I hope this helps.
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Frautoincnam
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PostPosted: Sun Apr 18, 2021 4:09 pm    Post subject: Reply with quote

pa4wdh wrote:
The mail server doesn't know if it's primary or secondary. It is only advertised as such in DNS.

I know all of that. that's not my question.
I don't ask how to create a MX backup.
I told 1) works.
Quote:
For that i left "mydestination" empty/default, because that would make it try to deliver that mail locally, which is not what you want.

that's why I put localhost in $mydestination. But I tried with dummy value, and empty.

Quote:
What you're searching for might be "relay_domains"

?
Did you really read my post ? I described my $relay_domains.


Quote:
To make sure you're not an open relay

Already done. But one more time, that's not the subject. I managed to configure my MX backup. The problem was about local delivery, but as told, solved.
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pa4wdh
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PostPosted: Sun Apr 18, 2021 4:29 pm    Post subject: Reply with quote

I'm sorry i didn't understand your question correctly, i'm just trying to help.

The only thing that seems to be missing from the configuration you posted is the "relay_host", it is set on your secondary mailserver and set something where it can reach the primary one.
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Frautoincnam
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PostPosted: Sun Apr 18, 2021 4:34 pm    Post subject: Reply with quote

Code:
# postconf relay_host
postconf: warning: relay_host: unknown parameter
# postconf relayhost
relayhost =

Missing because as default.
No need to specify, DNS is here for that. All mails to mydomain go to MX 10 when up.
But, one more time, relaying works !
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