How to send an Email to multiple recipients ?

It is easy to send email messages to more than one address. You can insert multiple addresses in the To: header field, or use the Cc: or Bcc: fields to add more recipients. When you insert multiple email addresses in any of these header fields, make sure you separate them correctly.
Use a Comma as a Separator
Most—not all—email clients require that you use a comma to separate multiple email addresses in any of their header fields.For these email providers, the correct way to separate email addresses in the header fields is:
[email protected],[email protected] [email protected]
and so on. For nine out of 10 email programs, commas are the way to go. They work fine unless you use Microsoft Outlook.
Outlook and any other email program that looks for names in the last name, first nameformat, where the program uses the comma as a delimiter, may run into problems if you separate email recipients with commas. Email clients that use commas as delimiters typically use semicolons to separate multiple addresses in their header fields. In Outlook, multiple addresses are entered with semicolon separators by default.
[email protected];[email protected];[email protected]
Switch to using the semicolon as a separator when in Outlook and you should be just fine. If you can’t get used to the switch or you frequently forget and get the name could not be resolved error message, you can change the Outlook separator to a comma permanently.
Change Outlook Separator to a Comma
In versions of Outlook beginning with Outlook 2010, you can change the preferences to use a comma in the headers rather than a semicolon by going to File > Option > Mail > Send messages. Check the box next to Commas can be used to separate multiple message recipients and you won’t need to bother with semicolons anymore.