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E-mail sub-addressing

We have always supported sub-addressing (or “tagging”) when receiving e-mails, by using the “+” sign. E.g. When using forwarding using an alias, up till now, this sub-address was replicated to the forwarded destination, e.g. gets forwarded to

As from now, this behavior is changed, the sub-address is now stripped from the forwarded destination. E.g. an e-mail to now gets forwarded to You can still use the sub-address in rules at e.g. Gmail, based on the (original) destination.

This change fixes some issues with forwards to mail-servers that don’t support sub-addressing, such as Microsoft Exchange.

Technically, this is implemented by changing the setting “propagate_unmatched_extensions” in Postfix from “canonical, virtual” to “canonical”.

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Monitoring of spam block-lists on Microsoft SNDS

Microsoft maintains its own block-lists for spam detection: Smart Network Data Services (SNDS).  They are used on,,, and any custom domain hosted on the Microsoft mail servers.  More information can be found here.

The Zabbix server at can now be used to monitor your IP-address on those lists.

The zabbix template is made public on my ZabbixCustomTemplates project on GitHub.