Microsoft Office 365: Email Limits / Retention

Message size 25 MB
Maximum number of recipients 500
Message send rate 30 messages per minute
Student mailbox size 50 GB
Employees mailbox size 50 GB
Emeriti mailbox size 50 GB
Honored retirees mailbox size 50 GB
Shared mailbox size (ie: 10 GB
Archive mailbox size 100 GB
Emails in Inbox and Subfolders No deletion schedule
Emails stored in Deleted Items folder 30 Days
Recover Deleted Items  14 Days
Spam folder items 30 Days