Software & Apps MS Office How to Separate Email Recipients With Commas in Outlook Commas are not used to separate email addresses by default in Outlook by Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated on March 17, 2020 MS Office Outlook Word Excel Powerpoint Tweet Share Email In most email programs, it's common practice to separate names of email recipients with commas. However, in Outlook, the semicolon is used to separate email recipients. If you'd rather use a comma, change the Outlook settings. Instructions in this article apply to Outlook 2019, 2016, 2013, 2010; Outlook for Microsoft 365; and Outlook Online. Why Comma Separators Don't Work in Outlook If commas are used to separate recipients in Outlook, a "name could not be resolved" message will appear. This means that Outlook doesn't understand the syntax used when typing the recipient addresses. Outlook interprets commas as separating the last name from a first name. For example, if you enter email@example.com, Mark, Outlook will read the recipient as Mark firstname.lastname@example.org. How to Make Outlook Allow Commas to Separate Multiple Email Recipients To have Outlook see commas when separating multiple email recipients: Go to the File tab and select Options. Select the Mail category. In the Send messages section, select the Commas can be used to separate multiple message recipients check box. Select OK. How to Allow Commas to Separate Multiple Email Recipients in Outlook.com Outlook.com automatically recognizes a comma between email addresses as the separator between contacts. In the To text box, enter an email address, then type a comma. Outlook.com searches for that contact in your contact list. If it finds it, it inserts the contact. If it doesn't find it, it accepts the email address you typed and places a box around it. When you finish adding recipient emails separated by commas, compose the message and select Send to finish.