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what is required to setup on email server to accept relay email from postfix installed on diff VM

US flag

[ServerA+postfix] --relay email--> [mailserver+companydomain.com] --send email--> ([email protected])

I need to set up an email alert sent from ServerA to the intended recipients mainly residing in the company domain. To achieve that, I installed Postfix in ServerA to relay the email to an external SMTP server and send the email to the users. I've configured the Postfix to relay the email but when i test sending email, the connection to SMTP server was timed out.

var/log/ mail.log

Jul 12 09:01:48 localhost postfix/postfix-script[7261]: starting the Postfix mail system
Jul 12 09:01:48 localhost postfix/master[7263]: daemon started -- version 3.5.18, configuration /etc/postfix
Jul 12 09:02:50 localhost postfix/pickup[7265]: 05568200EA: uid=0 from=<[email protected]>
Jul 12 09:02:50 localhost postfix/cleanup[7291]: 05568200EA: message-id=<[email protected]>
Jul 12 09:02:50 localhost postfix/qmgr[7266]: 05568200EA: from=<[email protected]>, size=376, nrcpt=1 (queue active)
Jul 12 09:03:21 localhost postfix/smtp[7293]: connect to smtp.server.com[server.ip.add]:587: Connection timed out
Jul 12 09:03:21 localhost postfix/smtp[7293]: 05568200EA: to=<[email protected]>, relay=none, delay=31, delays=0.02/0.03/31/0, dsn=4.4.1, status=deferred (connect to smtp.server.com[server.ip.add]:587: Connection timed out)
Jul 12 09:06:48 localhost postfix/qmgr[7266]: D366720278: from=<[email protected]>, size=376, nrcpt=1 (queue active)
Jul 12 09:07:18 localhost postfix/smtp[7360]: connect to smtp.server.com[server.ip.add]:587: Connection timed out
Jul 12 09:07:18 localhost postfix/smtp[7360]: D366720278: to=<[email protected]>, relay=none, delay=585, delays=554/0.02/31/0, dsn=4.4.1, status=deferred (connect to smtp.server.com[server.ip.add]:587: Connection timed out)

/etc/postfix/main.cf

smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
biff = no
append_dot_mydomain = no
readme_directory = no
compatibility_level = 2
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_security_level=may
smtp_tls_CApath=/etc/ssl/certs
smtp_tls_security_level=may
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = localhost.members.linode.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = localhost.members.linode.com, debian, localhost, localhost.localdomain, localhost
relayhost = [smtp.server.com]:587
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
#edited lines
smtp_sasl_auth_enable = yes
smtp_sasl_security_options = noanonymous
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_use_tls = yes
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

sasl_passwd

[smtp.server.com] [email protected]:password

Version: postfix (3.5.18-0+deb11u1) mailutils (1:3.10-3+b1)

I add the relayhost to point to SMTP server on port 587, then add multiple lines at the bottom to configure for the certificates. i also created a hash file for password authentication based on this article.

I was able to ping the mailserver from ServerA, but failed when telnet to mailserver on port 587 & 25. So i suspect this might be the port issue.

My concern is, what are need to be configured on the mailserver to make this to work?

ws flag
Please add your main.cf file (after stripping comments) advise what you have already changed in the file, the postfix version and where you sourced it from.
mangohost

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