On OnPremise, Sending email to multiple recipients doesn't work with SendEmail method

Question

Hi,
We are creating a site collection on OnPremise from App by using Sharepoint Client API's (16 version).
After creation of site collection, we are sending an email to all site collection administrators. But we found that email is being sent to the only first person mentioned in the "To" list. For sending email we are using following method "Microsoft.SharePoint.Client.Utilities.Utility.SendEmail()".
We tried different scenarios by passing alternately domain username and email address.
Here are the findings for the different scenarios for the "To" field:
1) "domain\user1; domain\user1" => sends email to first user
2) "[email protected]; [email protected]" => sends email to both emails (at least shows in inbox To field, two occurances of email)
3) "domain\user1; domain\user2" => sends email to first user
4) "[email protected]; [email protected]" => sends email to first user
Here is the code we are using:
                EmailProperties properties = new EmailProperties();
                properties.To = to.ToList();
                if (cc != null)
                    properties.CC = cc;
                properties.Subject = subject;
                properties.Body = body;
                Utility.SendEmail(context, properties);
                context.ExecuteQuery();
Please let us know what is going wrong here.
Thanks in advance for your valuable inputs.
Br,
Shriram
Shri07

Answer 1

According to the R16 Admin preview guide;-
"Send Email to Multiple Recipients
Expression Builder is now linked to the email address text field that is presented when the Specific Email Address
option is selected. Workflow administrators can enter multiple email addresses directly, or click the "fx" icon
beside the field, and use Expression Builder to define expressions that evaluate to one or more email addresses.
The benefit of this feature is that emails can be stored on any text field in the base record and multiple emails can
be sent using one workflow action. "
But how that works exactly is not clear, I have tried commas, semi-colons, spaces, apostrophes, doublequotes, to separate and try to establish the correct syntax without luck.
Bob - Perhaps you can do some digging and find out the correct syntax for multiple addresses?