Microsoft Outlook is the university's default email system for faculty, staff, and affiliates. It is a cloud-based service that manages email, calendars, task lists, and address books.

Accessing Email

• Email software: Outlook on the web (recommended) or Microsoft Outlook (desktop). See our Choose an Email Client article.
• Mobile devices: works with Android, iOS, Windows Phone, and other devices that support ActiveSync. See how to get connected with your iOS device or how to get connected with your Android or other device.
• Deleted Items retention: Messages remain in your Deleted Items folder for 30 days and are then automatically deleted.

Important Size Limits

These limits vary based on many factors. The numbers below reflect what most individuals will need, using Outlook on the Web and day-to-day email use. For more details, refer to Outlook and Microsoft 365 Mailbox Limits.

• Mailbox size 50 GB.
• Message size limit 112 MB (total size including attachments). The limit applies for both outgoing and incoming messages. See Attachments Not Getting Through for details.
• Maximum number of attachments on a single message 250.
• Maximum number of recipients per meeting invite and cancellations 2,500 per day.
• Maximum subject length 255 characters.

Limits on Sending Very Large Mailings

Microsoft 365 includes some security defenses that limit the ability of an individual to send huge numbers of messages in a short amount of time. If you have legitimate large mailings to do, please understand these limits and the alternatives you have for delivering your messages.

• Maximum number of addresses allowed in the To, Cc, and Bcc fields (combined): 500 per message
• Maximum number of messages that can be sent from your email client per minute: 30
• Maximum number of recipients who can receive messages sent from your account (or a Resource Account) in a 24-hour period: 10,000 (and no more than 5,000 can be to external addresses (that is, addresses other than @cornell.edu).

Notes

• The 24-hour period is a rolling window: for example, if you send messages to 2,000 recipients at 8:30am, then messages to 5,000 recipients at 12 noon, then messages to 2,000 recipients at 2:30pm, and messages to 1,000 recipients at 4pm, you won't be able to send any more messages until 8:30am the next day.
• If you try to send a message after exceeding the limit, you will either see an immediate error about the recipient limit, or the message will be returned to you with an error. Save the message to your Drafts folder and try again later.
• A message will only be delivered if it can be delivered to all the recipients without going over the 10,000 limit. For example, if you've already sent messages to 9,900 recipients, and you attempt to send one message to 150 recipients, the second message will not be delivered because it would be 50 recipients over your limit for the 24-hour period.

Alternatives for Very Large Mailings

• Students, staff, and faculty can create and use one or more e-lists: a good choice if you'll email these same individuals many times and they're not all at Cornell.
• Staff and faculty can request and use a CornellAD mail-enabled group: a good choice if these individuals are all at Cornell and you'll email these same individuals many times (a mail-enabled CornellAD group is only counted as one recipient).
• Staff and faculty can use bulkmail: a good choice if you are sending an announcement not starting a conversation.
• Thinking about using an external vendor to distribute official Cornell messages? Please read our article about using third-party senders.