Maximum Number of Addresses in a Microsoft Mail Group

By Timothy Smithee

Email everyone at the event using a single Contact Group address.
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Microsoft Outlook allows you to create Contact Groups, also known as distribution lists or email groups. If you routinely send email to the same group of people, setting them up as a Contact Group allows you to save time by sending the email to the group instead of entering all the addresses. You can also create a Contact Group that contains other Contact Groups. In most cases, there is no limit to the number of email addresses you can have in a Contact Group.

Older Versions of Outlook

Outlook 2010 and later have no limit on the number of addresses you can include in a Contact Group. In earlier versions, the maximum number of addresses you can include in a Contact Group depends on the amount of information stored for each contact. Typical limits are between 50 and 70 contacts, but can be as low as 25. A Contact Group may stop working if you include additional contact information for the members, in which case you can split the group into two Contact Groups.

Exchange and Other Mail Servers

Even though the number of addresses in a Contact Group is unlimited, the mail server may have limits. In a corporate environment, the Microsoft Exchange server may have maximum sizes for Contact Groups. In home and small business environments, your Internet Service Provider may block emails that contain more than a specified number of addresses. In addition, emails that contain a large number of addresses may be marked or blocked as spam by the recipients' email provider or client software.

Privacy and Readability

When you send an email to a Contact Group, Outlook replaces the group name with the email addresses of everyone in the group, so that all the recipients see everyone's email address. This may take up a lot of space at the top of the email, and also raises privacy concerns. If the group is, for example, a gaming club and all the members know each other, this is fine; but if the group members do not know each other, sending everyone in the group the email address of everyone else in the group could be a serious and even illegal violation of privacy. To avoid this, use the BCC field, not the TO field, when sending to a Contact Group.

Contact Group vs. Mailing List

A Contact Group is a convenient way for one person to routinely send email to a group or groups of people. However, if a large group of people frequently needs to send email to each other, and particularly if privacy is desired, a subscriber discussion list or mailing list program is a better way to go, as these are Web-based programs that allow any member to send an email to a group, using a single email address.