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Outlook - FAQ

General FAQ

Sometimes I need to send emails to large numbers of people. Does Outlook limit the number of emails I can send?

Yes, Outlook limits the number of recipients per message to 500 and sets a daily recipient limit of 10,000 recipients. If you have email sending needs that exceed these limits, we recommend using one of CU Boulder's bulk/mass email communication services.

Are certain attachments types blocked by Microsoft 365?

Outlook and Outlook on the web do not allow you to receive files of certain types (such as .exe files) as attachments, because of their potential for introducing a virus into your computer. By default, Outlook blocks these files.

For a full list of file types, please review Microsoft's blocked attachments page.

How much storage space does my Microsoft account have?

All Microsoft 365 accounts by default have 50GB of Storage for email and calendar data. Please note: This limit cannot be increased.

Visit the Outlook on the web Check Mailbox Usage tutorial to learn how to check the capacity of your mailbox or use Microsoft's Manage My Mailbox Size page for additional help. 

How long do messages stay in the Deleted Items folder?

The deleted items folder retention period is 30 days. After that, messages are automatically removed from the folder. Items that have been automatically removed from the Deleted Items folder are retained for 30 days before being permanently deleted. You can recover items during the retention period using Outlook or OWA. Visit the Recovering Deleted Items tutorial for instructions. 

What do I need to know if I use delegates to manage my Calendar?

OIT has created an Outlook Calendaring Best Practices guide to provide guidance to Exchange Online calendar users on the practices and email/calendar clients that best avoid calendaring problems. They have been collected from many years of experience with Exchange and from multiple sources. 

What is Microsoft Defender Quarantine?

Microsoft Defender Quarantine is a feature that is integrated with Outlook to protect users from harmful emails and spam. It automatically holds suspicious emails in quarantine until the user can review them and decide whether to allow them to be delivered to their inbox or to delete them. 

By enabling Defender Quarantine on the Outlook client, OIT is empowering end users to release messages they previously would not have seen. Learn more on the Microsoft Defender Quarantine page.