Configuring Postfix to use port 587

Oct 13, 2025 by wbrum.org 0 views

Introduction

Sending emails from a virtual machine (VM) hosted on Google Cloud Platform (GCP) can be a challenging task, especially when port 25 is blocked. In this scenario, using port 587 is a viable solution. However, to send emails on port 587, you need to configure your email server, specifically Postfix, to use this port. In this article, we will discuss the necessary steps and requirements to send emails on port 587.

Requirements

To send emails on port 587, you need the following:

Postfix: A popular open-source mail transfer agent (MTA) that can be used to send and receive emails.
Google Cloud Platform (GCP): A cloud computing platform that provides a virtual machine (VM) to host your applications.
Port 587: A non-encrypted port used for sending emails, also known as submission port.
SMTP (Simple Mail Transfer Protocol): A protocol used for sending emails between mail servers.

Configuring Postfix to use port 587

To configure Postfix to use port 587, you need to edit the Postfix configuration file. The location of this file may vary depending on your Linux distribution. In most cases, it is located at /etc/postfix/main.cf.

Step 1: Edit the Postfix configuration file

Open the Postfix configuration file using a text editor, such as nano or vim. You can use the following command to open the file:

sudo nano /etc/postfix/main.cf

Step 2: Configure Postfix to use port 587

In the Postfix configuration file, you need to add the following lines to configure Postfix to use port 587:

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no
append_dotlock_file = no
readme_directory = no
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
message_size_limit = 10240000
smtpd_helo_required = yes
smtpd_helo_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_hostname, reject_invalid_hostname, reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unauth_pipelining
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_unauth_pipelining
smtpd_sender_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_sender, reject_unknown_sender_domain
smtpd_client_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_sender, reject_unknown_sender_domain
smtpd_data_restrictions = reject_unauth_pipelining
smtpd_milters = 
non_smtpd_milters = 
milter_default_action = accept
milter_protocol = smtpd_milter_protocol
smtpd_tls_auth_only = yes
smtpd_tls_security_level = may
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong<br/>
**Q&A: What do I need to send emails on port 587?**
=====================================================
Q: What is port 587 and why do I need it?
A: Port 587 is a non-encrypted port used for sending emails, also known as submission port. You need it because Google Cloud Platform (GCP) blocks port 25, and using port 587 is a viable solution to send emails from your VM hosted on GCP.
Q: What is Postfix and why do I need it?
A: Postfix is a popular open-source mail transfer agent (MTA) that can be used to send and receive emails. You need it because it allows you to configure your email server to use port 587.
Q: How do I configure Postfix to use port 587?
A: To configure Postfix to use port 587, you need to edit the Postfix configuration file. The location of this file may vary depending on your Linux distribution. In most cases, it is located at /etc/postfix/main.cf. You need to add the following lines to configure Postfix to use port 587:
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no
append_dotlock_file = no
readme_directory = no
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtpd_tls_dh1024_param_file = /etc/ssl/certs/dhparam.pem
smtpd_tls_eecdh_grade = strong
smtpd_tls_random_bytes = 32
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_note_starttls_offer = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = kEDH,kDES,kCDH
smtp</code></pre>


                
                    
                        

                    
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