Misconfigured Plesk hosts in XBL
Misconfigured Plesk hosts in XBL
Misconfigured Plesk hosts can have unexpected outcomes – the behavior of such a host closely mimics the behavior of a certain type of spambot.
Plesk’s online guide describes the “Outgoing mail mode” option and its three settings:
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- Send from domain IP addresses:
By default, mail from each domain is sent from the domain’s IP address. The host name used in the SMTP greeting is the Plesk server host name specified in Tools & Settings > Server Settings. Selecting this option may result in mail sent from some or all domains being marked as spam if the Plesk server host name fails to resolve properly, or if the domain’s IP is different from the one to which the Plesk server host name resolves.
This option works best if it is required to have a single IP address on the Plesk server.
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- Send from domain IP addresses and use domain names in SMTP greeting
If selected, Plesk changes the mail server configuration so that the SMTP greeting contains the name of the domain from which the email message is sent.
Warning: Selecting this option may result in mail sent from some or all domains being marked as spam if the destination mail server uses Spamhaus XBL and more than one domain on the Plesk server uses the same IP address.
In addition, selecting this option on Plesk servers hosting a large (more than 100) number of domains will likely result in significantly increased server load.
This option works best if a dedicated IP address is allocated to every domain hosted on the Plesk server, and the number of domains hosted on the server is not very large.
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- Send from the specified IP adresses:
If it is required to use certain IPv4 and IPv6 addresses for all outgoing mail.
If None is selected, outgoing mail will not be sent.
The first setting is shown as ‘enabled’ circled in red in the screen shot below:
We recommend you use the first or third option in virtually all cases.
The second option, “send from domain IP addresses and use domain names in SMTP greeting” can lead to reputational and XBL issues, and should be used with extreme care:
- Many Plesk installations are unable to bind to different IP addresses to send email on behalf of each hosted domain. This is especially true if the web server uses a single IP address to host multiple domains by “virtual host” – there are no other addresses to bind to, so, it’s using the same IP address all the time.
- The “send from domain IP addresses and use domain names in SMTP greeting” option should only be used if you’re certain your installation can successfully bind to specific outbound IP addresses, and that each IP address will only be used for at most 2-3 different domains.