I am a beginner in configuring mail delivery systems. Recently, orders came from the management that we need to send confirmation emails to our clients whenever they complete their applications (I work at a local college).
Upon scrambling good ol' Google for answers, I found this article at DigitalOcean on how to configure a 'send-only' Postfix (https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-22-04), which is exactly what I need since the parameters of the orders from the management is that the emails should be no-replies.
I found no hiccups on following the instructions in the said link, EXCEPT:
Apr 16 08:53:03 application postfix/pickup[360142]: DA25140A2775: uid=0 from=<[email protected]>
Apr 16 08:53:03 application postfix/cleanup[360716]: DA25140A2775: message-id=<[email protected]>
Apr 16 08:53:03 application postfix/qmgr[360143]: DA25140A2775: from=<[email protected]>, size=415, nrcpt=1 (queue active)
Apr 16 08:53:34 application postfix/smtp[360718]: connect to gmail-smtp-in.l.google.com[74.125.204.27]:25: Connection timed out
Apr 16 08:53:49 application postfix/smtp[360718]: connect to alt1.gmail-smtp-in.l.google.com[142.250.141.26]:25: No route to host
Apr 16 08:54:04 application postfix/smtp[360718]: connect to alt2.gmail-smtp-in.l.google.com[142.250.115.27]:25: No route to host
Apr 16 08:54:34 application postfix/smtp[360718]: connect to alt3.gmail-smtp-in.l.google.com[64.233.171.27]:25: Connection timed out
Apr 16 08:55:04 application postfix/smtp[360718]: connect to alt4.gmail-smtp-in.l.google.com[142.250.152.26]:25: Connection timed out
Apr 16 08:55:04 application postfix/smtp[360718]: DA25140A2775: to=<[email protected]>, relay=none, delay=121, delays=0.46/0.01/121/0, dsn=4.4.1, status=deferred (connect to alt4.gmail-smtp-in.l.google.com[142.250.152.26]:25: Connection timed out)
... which I found on the system log after running the test command indicated in the instructions. (I altered the domain and the email address for privacy purposes.)
My Postfix Configuration is:
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no
append_dot_mydomain = no
readme_directory = no
compatibility_level = 3.6
smtpd_tls_cert_file=/etc/letsencrypt/live/college.ph/cert.pem
smtpd_tls_key_file=/etc/letsencrypt/live/college.ph/privkey.pem
smtpd_tls_security_level=may
smtp_tls_CApath=/etc/ssl/certs
smtp_tls_security_level=may
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = college.ph
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = college.ph
relayhost =
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = loopback-only
inet_protocols = ipv4
mynetworks = 127.0.0.1/32
By the way, I configured Postfix to listen on port 3000/TCP since our ISP blocks the shit out of port 25. Port-forwarding, as well as SPF and DMARC is in place.
What am I doing wrong? Thank you very much in advance.
