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Twitter- Server operating system version
- Ubuntu 22.04 LTS (64-bit)
- Plesk version and microupdate number
- Plesk Obsidian 18.0.70 and MU 3
I’m currently troubleshooting an intermittent email delivery problem on a server running Plesk Obsidian for Linux. The domains hosted on the server have working websites, and incoming mail appears to be functioning normally, but outgoing messages are not consistently being delivered. In some cases, an email sends successfully without any noticeable delay, while at other times the application or mailbox reports an SMTP connection or delivery failure. The issue does not seem to affect every message, which makes it difficult to determine whether the problem is related to Postfix, the mail service configuration, or something happening at the server/network level.
I have already checked the usual DNS and authentication settings for the affected domain. The domain has SPF, DKIM, and DMARC records configured, and the corresponding mail settings in Plesk appear to be enabled correctly. I have also verified that the mail service is running and that the affected mailboxes have sufficient storage space. What is confusing is that the configuration does not appear to change between successful and failed attempts. When the same sender sends another message later, it may work normally, so I’m wondering if there could be an intermittent connection issue between Postfix and the remote SMTP servers rather than an incorrect DNS or authentication configuration.
The main difficulty is finding useful information in the Plesk interface because the failure is not always reproduced consistently. I have started checking the mail logs around the exact time of failed messages, but I’m not sure which entries would be most important to focus on when distinguishing between a remote rejection, SMTP timeout, DNS resolution problem, connection refusal, or a local Postfix queue issue. I also want to avoid making random changes to the mail configuration because the server does successfully send some messages and I don’t want to introduce another problem while troubleshooting this one.
Has anyone experienced this type of intermittent outgoing-mail failure with Plesk Obsidian for Linux? I would appreciate advice on the best way to trace one failed message from the application or mailbox through Postfix and determine exactly where the delivery process is breaking. In particular, I’d like to know which Plesk/Postfix logs and commands I should check, and whether there are any Plesk-specific settings that commonly cause intermittent SMTP connection or delivery problems when SPF, DKIM, and DMARC are already configured correctly.
I have already checked the usual DNS and authentication settings for the affected domain. The domain has SPF, DKIM, and DMARC records configured, and the corresponding mail settings in Plesk appear to be enabled correctly. I have also verified that the mail service is running and that the affected mailboxes have sufficient storage space. What is confusing is that the configuration does not appear to change between successful and failed attempts. When the same sender sends another message later, it may work normally, so I’m wondering if there could be an intermittent connection issue between Postfix and the remote SMTP servers rather than an incorrect DNS or authentication configuration.
The main difficulty is finding useful information in the Plesk interface because the failure is not always reproduced consistently. I have started checking the mail logs around the exact time of failed messages, but I’m not sure which entries would be most important to focus on when distinguishing between a remote rejection, SMTP timeout, DNS resolution problem, connection refusal, or a local Postfix queue issue. I also want to avoid making random changes to the mail configuration because the server does successfully send some messages and I don’t want to introduce another problem while troubleshooting this one.
Has anyone experienced this type of intermittent outgoing-mail failure with Plesk Obsidian for Linux? I would appreciate advice on the best way to trace one failed message from the application or mailbox through Postfix and determine exactly where the delivery process is breaking. In particular, I’d like to know which Plesk/Postfix logs and commands I should check, and whether there are any Plesk-specific settings that commonly cause intermittent SMTP connection or delivery problems when SPF, DKIM, and DMARC are already configured correctly.
