Send email at a later time - microsoft-graph-api

Question

I am wondering if the /v1.0/me/sendMail has the ability to delay sending an email. In the Outlook client, you can specify that you want your email sent at a later date and time. I've snooped around to see if there is a property that can be set on the message object to indicate this.
Did anyone find a way to get this working? Of course, I could implement something in my software to handle the delayed sending, but why re-create something if it is already there.

Answer 1

You can achieve delayed sending of emails using extended properties. These can be set on the Graph API request payload using the "singleValueExtendedProperties" attribute.
The property to use is PidTagDeferredSendTime which has the ID 0x3FEF and type SystemTime.
The id attribute of "singleValueExtendedProperties" takes different formats depending on the property you are setting.
For the deferred send time you would use SystemTime 0x3FEF.
Example using a HTTP JSON POST Payload:
{
"message": {
"subject": "Meet for lunch?",
"body": {
"contentType": "Text",
"content": "The new cafeteria is open."
},
"toRecipients": [
{
"emailAddress": {
"address": "bob#contoso.com"
}
}
],
"singleValueExtendedProperties":
[
{
"id":"SystemTime 0x3FEF",
"value":"2019-01-29T20:00:00"
}
]
}
}
Example using the Microsoft Graph API client library:
var client = /* Create and configure GraphServiceClient */;
var msg = new Message();
msg.ToRecipients = List<Recipient>();
msg.ToRecipients.Add(new Recipient() {
EmailAddress = new EmailAddress() { Address ="bob#contoso.com" }
};
msg.Subject = "Meet for lunch?";
msg.Body = new ItemBody()
{
Content = "The new cafeteria is open.",
ContentType = BodyType.Text,
};
msg.SingleValueExtendedProperties = new MessageSingleValueExtendedPropertiesCollectionPage();
msg.SingleValueExtendedProperties.Add(new SingleValueLegacyExtendedProperty()
{
Id = "SystemTime 0x3FEF",
Value = DateTime.UtcNow.AddMinutes(5).ToString("o")
});
await client.Me.SendMail(msg, true).Request().PostAsync();

Answer 2

https://gallery.technet.microsoft.com/office/Send-Emails-until-a-9cee20cf
You set the deferred send time extended prop when creating the item.