- Plesk for Linux
- Plesk for Windows
Unable to send and forward emails from Plesk server to external servers either completely or intermittently, causing mail queue to fill up.
Emails cannot be sent by using PHP script.
Emails between domains served by Plesk can be sent.
One of the following errors may be found in
CONFIG_TEXT: postfix/smtp: E3B24978700: firstname.lastname@example.org, relay=none, delay=537, delays=446/0.02/91/0, dsn=4.4.1, status=deferred (connect to example.com[203.0.113.2]:25: Connection timed out)
CONFIG_TEXT: postfix/smtp: connect to example.com[203.0.113.2]:25: Connection timed out
CONFIG_TEXT: postfix/smtp: E3B24978700: email@example.com, relay=none, delay=537, delays=446/0.02/91/0, dsn=4.4.1, status=deferred (connect to example.com[203.0.113.2]:25: Connection refused)
CONFIG_TEXT: qmail: 1491974064.856278 delivery 8214: deferral: Sorry,_I_wasn't_able_to_establish_an_SMTP_connection._(#4.4.1)
On Windows the error below may be found in MailEnable > Servers > localhost > Services and Connectors > SMTP > Logs > Debug > SMTP-Debug-xxxx.log:
CONFIG_TEXT: ME-E0038: [FFEFCD05AA0A4CE9B2E74C7CAA6D8FE5.MAI] Communications Error: Socket connection to mx1.example.net failed (error 10060). The host was either not contactable or it rejected your connection. Socket Family = 2; Host=203.0.113.2; Port=25
Note: There might be a Smart Host configured for SMTP.
The firewall on the Plesk server does not restrict connections to port 25.
Outbound connections via port 25 from Plesk server are restricted either completely or intermittently:
# telnet smtp.gmail.com 25
telnet: connect to address 203.0.113.2: Connection refused
Port 25 is blocked for outbound connections.
Sometimes internet service providers (ISP) can restrict or limit outbound/inbound connections on port 25 due to security reasons. Also, the Google Cloud platform has such port blocked by default, and services like Google Workspace (former G Suite) should be used to send mail.
Note: Networking tasks and the local firewall configuration are the activities that should be handled by the Plesk server administrator, as Plesk is a part of the server infrastructure and relies on local network settings.
Note: Once port 25 is opened by your hosting/cloud provider and mail starts to work, you may safely close the message about TCP port 25 is blocked in Plesk at Tools & Settings > Mail Server Settings.
Note: For an example of mail relay configuration, refer to our official Udemy course.
Here are the general troubleshooting steps:
Make sure that the local firewall does not cause the issue. Stop the service temporarily and try to send mail or open mail port under Plesk > Tools & Settings > Firewall;
If the issue still persists, it means that the cause is outside of the Plesk server. In that case, contact the network administrator and discuss if port 25 can be added to the allowed ones or not.
If any of the Cloud Services are used, it is needed to check the firewall on the Cloud Service’s side.
|Cloud Provider||References to unlock SMTP ports|
Outbound connections to port 25 are limited by default to prevent outgoing spam.
outbound connections to port 25 are limited by default to prevent outgoing spam.
|Microsoft Azure||Azure blocks port 25 for new users.
Submit a request by using the following link:
Subscription Management Problem type: Request to enable Port 25 email flow
|Use a third-party service like SendGrid. Create a SendGrid account and configure Postfix to use SendGrid as a relay.|
|Vultr||To unlock port 25 follow: https://www.vultr.com/docs/what-ports-are-blocked|
|Nitrado||Block the ports 25, 465 and 587 by default but can unlock them (see point 3) https://server.nitrado.net/eng/pages/cloud_server_tos|
|OVH||Configure firewall on port 25: https://docs.ovh.com/ca/en/dedicated/firewall-network/|
Alibaba ECS instances
|Apply the form to enable TCP port 25.|
Ports 25, 465 and 587 can be unlocked:
||Linodes on newly created customer accounts will have connections from ports 25, 465, and 587 blocked by default.|
Contact DigitalOcean support