Can not send or receive email on my cento7 postfix Mailserver

Question

Hi,we try to build a public postfix mail server on a centos7 machine.all test on the internet give no error. But I could not send or receive email only if i add 0.0.0.0/0 to mynetwork line:mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 160.242.193.8/29 0.0.0.0/0 I know i shouldn’t do that.here my /etc/postfix/main.cf: See /usr/share/postfix/main.cf.dist for a commented, more complete version Debian specific: Specifying a file name will cause the first line of that file to be used as the name. The Debian default is /etc/mailname. #myorigin = /etc/mailname smtpd_banner = $myhostname ESMTP $mail_name (CentOS)biff = no appending .domain is the MUA’s job. append_dot_mydomain = no Uncomment the next line to generate “delayed mail” warnings #delay_warning_time = 4h readme_directory = no TLS parameters smtpd_tls_cert_file=/etc/letsencrypt/live/mymailserver.com/fullchain.pemsmtpd_tls_key_file=/etc/letsencrypt/live/mymailserver.com/privkey.pemsmtpd_use_tls=yessmtpd_tls_auth_only = yessmtp_tls_security_level = maysmtpd_tls_security_level = maysmtpd_sasl_security_options = noanonymous, noplaintextsmtpd_sasl_tls_security_options = noanonymous See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for information on enabling SSL in the smtp client. smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destinationsmtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destinationsmtpd_sender_restrictions = reject_unknown_sender_domainmyhostname = mymailserver.com alias_maps = hash:/etc/aliasesalias_database = hash:/etc/aliasesmydomain = mymailserver.com myorigin = $mydomainmydestination = $mydomain, localhost, mail, mail.$mydomainrelayhost =mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 160.242.193.8/29mailbox_size_limit = 0recipient_delimiter = +inet_interfaces = allinet_protocols = all Handing off local delivery to Dovecot’s LMTP, and telling it where to store mail virtual_transport = lmtp:unix:private/dovecot-lmtp Virtual domains, users, and aliases virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-mailbox-domains.cfvirtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-mailbox-maps.cfvirtual_alias_maps = mysql:/etc/postfix/mysql-virtual-alias-maps.cf,mysql:/etc/postfix/mysql-virtual-email2email.cf please will you help me to solve the issue.Best regardsRachid

KFSys · Answer

Heya,

Checking the logs, you can see the following errors after some messages:

:25: Connection timed out

port 25 is closed for external use. There are a few ways to go about the problem

try using ports like 465 or 587 for SMTP
use a third party solution only for your E-mails. Good examples are sendgrid.

To expand more on blocking port 25 for new accounts, this is something DigitalOcean has been doing to reduce spam on it’s network. It is more that we simply cannot accurately determine who is going to send it.

Stopping spam is a constant fight, so DigitalOcean has implemented some restrictions on newer accounts. Having said that, you can always contact them and ask for the port block to be lifted on:

https://www.digitalocean.com/support/

More information here:

https://docs.digitalocean.com/support/why-is-smtp-blocked/

Hope that helps!