Below are some of the limits for Office 365 accounts - see more detailed information can be found at Exchange Online Limits  

LIMIT TYPE Outlook (Windows) OWA Outlook (Mac)
Attachment size limit (sending and receiving) - The default maximum quota for receiving is 30MB.  Also, when you attach a file to a message, the file size of the attachment increases (it can increase as much as 30% in size when it is sent).   30 MB 30 MB 30 MB
Message size limit -  Keep in mind that someone's mailbox on the Office 365 server will be prohibited from receiving messages if they exceed their maximum quota limit.  150 MB 112 MB 35 MB
Address List Limit 1000 1000 1000
Storage - User Mailbox, Shared Mailbox, Resource Mailbox, Public Folder Mailbox 50 GB 50 GB 50 GB
Recipient Limit per message 500 500 500

Quota Alerts Across Office 365:

Warning: 49GB 

Prohibit Send: 49.5 GB 

Prohibit Send/Receive: 50GB

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Last updated: 
March 8, 2017