XOORG Server Support

[ml1nk]

These changes allows the smtp server to advertise XOORG capability and extract it into the options. There is a simple test case added and it is tested against Exchange Online with a Outgoing Connector.

Some information about XOORG and it's usages:
https://techcommunity.microsoft.com/t5/exchange-team-blog/advanced-office-365-routing-locking-down-exchange-on-premises/ba-p/609238

I will also add XOORG client support next week, to be able to use it in combination with a Exchange Online Inbound Connector.

[emersion]

Sorry, I'd rather not maintain some Microsoft-specific proprietary features.

[ml1nk]

I understand your reasoning behind it, but I would argue that

• the changes in the server (and client later on) are very small without anything special, so there is no big maintenance to be done
• it's a non-standard but well documented extension which is very helpful in O365/Hybrid Exchange environments whenever you need to work with connectors
• it's hidden behind a flag, so no harm is done if not used