Symptoms
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Unable to receive and send mails from Plesk hosted on DigitalOcean, IONOS, Amazon Lightsail, AWS EC2 or Microsoft Azure instance.
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Outgoing mail connections via 25 port are not possible, the following error can be found in
/var/log/maillog:dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[142.250.4.26]:25: Connection timed out)
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The following error can be found in
%plesk_dir%Mail ServersMail EnableLogging:Communications Error: Socket connection to gmail-smtp-in.l.google.com failed (error 10060). The host was either not contactable or it rejected your connection. Socket Family = 2; Host=203.0.113.2; Port=25
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It is possible to send out an email message locally (to a mailbox in Plesk).
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The following warning can be seen in Tools & Settings > Mail Server Settings:
You cannot send emails from Plesk because outbound connections on TCP ports 25 and 587 are blocked. Check the firewall settings or contact your hosting provider. If you are sure that the ports are already open, Plesk can recheck them. Start the recheck
Cause
The SMTP port 25 (default for mail relaying even nowadays) is blocked by a firewall that resides on a level above the server on the side of DigitalOcean, IONOS, Amazon or Azure.
Resolution
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For AWS instance, submit a request to AWS support to have port 25 unblocked in accordance with Amazon documentation or set up mail relay as shown in our free Udemy course.
Warning: If you have Amazon Lightsail please explicitly mention in the link above that you need to remove the port block for LightSail, otherwise the AWS team will remove it for EC2 only.
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For Microsoft Azure, contact support at Subscription Management Problem type: Request to enable Port 25 email flow.
- For IONOS, SMTP port 25 (outgoing) is blocked on a level above the server for security reasons by default. The only way to unblock it is to contact their support, as explained in the following article:
Setting Up Email on a Server With Plesk - IONOS Help - For DigitalOcean, SMTP port 25 is blocked on a level above the server for security reasons by default. The only way to unblock it is to contact their support, as explained in the following article:
Why is SMTP blocked? | DigitalOcean Documentation -
If the Plesk Firewall is used, open mail port under Plesk > Tools & Settings > Firewall.
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If the system or a third-party firewall is active on the server, make sure that it is not blocking the connection to the 25, 465, 993 and 995 ports.
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In case of an intermediate firewall, it is required to contact the service provider.
Additional information
Unable to send emails using Plesk local mail server: Connection timed out or connection refused. (#4.4.1)
Which Ports Need To Be Opened for all Plesk Services to Work with a Firewall?