"Exchange Online customers who need to send legitimate bulk commercial email (for example, customer newsletters) should use third-party providers that specialize in these services. They have stated that Office 365 is not meant to be a bulk email service. such as or Gmail, the combined file size limit is 20 megabytes (MB) and for Exchange accounts (business email. This limit prevents your computer from continually trying to upload very large attachments that exceed the limits of most Internet service providers. NOTE: Microsoft has implemented Receiving and Sending Limits. Outlook limits the size of files you can send. Storage - User Mailbox, Shared Mailbox, Resource Mailbox Note: 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). Message send/receive size limit (including attachments) - 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. The University of Iowa supports Microsoft OneDrive for Business which allows for file sizes larger than 150mb. Whenever possible, it is advised to use a file collaboration tool for large files.While the UI email systems allow sending and receiving 150mb email messages (including attachments), other external email systems continue to have smaller limits. Know about email attachemnt size limit in your Microsoft Hotmail account.Email attachments count against overall email storage quota.If you’re using Outlook in a business environment and use SharePoint, you can save a file. This can increase the time required to send the message. Question: Q: The total attachment size exceeds the 25MB limit. Attaching a large file to an email message requires uploading that file to the email system.This includes both the message content and attachments. Maximum total message send/receive size is 150mb.This change is being made to allow easier collaboration within the University of Iowa. Starting Monday, February 5, 2018, both Office 365 and UI Healthcare email systems increased the maximum message send/receive limits to 150mb. Below are some of the limits for Office 365 accounts - more detailed information can be found at Exchange Online Limits