Change Site Policy Deletion notification email template in SharePoint

The Site Policies in SharePoint are information management tool that helps you implement some site life cycle management. Whether this is dictated by internal house keeping rules or some external regulations that apply to your organisation, the Site Policy is the out of the box way to go if you want to "close" a site, delete it or both, automaticaly after certain period of time.

With site policies you have the option to notify the site owners in advance before the site is deleted. The mail looks like the one below.

The information in this email might not be suitable for your organization.

Fortunately there is a way to change the default Site Policy notification email body template and the email subject. This is not done in some XML template file like the Alerts template, maybe there is one, but I have not found it. There is SSOM and CSOM API that you can use to set custom email body template per policy.

The documentation of this is very poor and the best resource on this is the article Site Policy in SharePoint.

Unfortunately I have not managed to make this work server side or using PowerShell. I have tried with SharePoint 2013, SharePoint 2016 and SharePoint Online ssom and csom as well.

The only way I found it working is from console application using the CSOM approach.

The site policy post above is good and the code should work as it is, but it has some gaps.

There are three placeholders that we can use, placeholders for Site Url, Deletion Date and Mailbox Id.
However the placeholders with curly braces that are demonstrated in the post will not work.

I would like to save you some time testing especially if you are targeting SharePoint Online, as there you cannot manually run the "Expiration Policy" timer job.

The correct placeholders are below, without curly braces or any spaces.

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SiteUrl: <!--SiteUrl-->
Deletion Date: <!--SiteDeleteDate-->
Mailbox ID: <!--TeamMailboxID-->

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I hope you found this helpful!