Send email to multiple recipients using win32com module in Python
Try separating by semicolons:
newMail.To = 'Amy; john; sandy'If you do a web search for "outlook interop createitem" you can find the docs for MailItem.To where this is explained.
Update: this is not an Outlook script, it is a Python script that uses Python's win32com module to control Outlook. The docs I'm referring to are the VB/C# docs for Outlook's COM interface (for example the possible values of OlItemType).