Summary of Office 365 Limitations
- The maximum number of devices connected to a mailbox is 10.
- The maximum total size of an e-mail message. The total size includes the message header, the message body, and any file attachments is 25MB
- The maximum number of file attachments allowed in an e-mail message is 125 attachments
- The maximum number of text characters allowed in the subject line of an e-mail message is 255 characters
- The maximum number of message body parts that are allowed in a MIME multipart message is 250 parts
- The maximum number of forwarded e-mail messages that are allowed in an e-mail message is 30 messages
- The maximum number of message recipients allowed in the To:, Cc:, and Bcc: fields is 500 recipients
- The maximum number of e-mail messages that can be sent from a single e-mail client per minute. The client is identified by the user account is 30 messages per minute
- The maximum number of recipients that can receive e-mail messages sent from a single cloud-based mailbox in a 24 hour period is 1500 recipients in a day.