Email Limits: What Are the Email Sending Limits of My Microsoft 365 Mailbox? - FAQs

Q: What are the different limits?

A: There are two different types of limits.

Recipient Limit - The number of unique email addresses that can be added to the To, Cc, and Bcc fields in a single email.
Recipient Send Rate Limit - The number of emails that can be sent from any one account over a specific time period. Limit exists for both per hour and per day.

Q: Which groups are affected by the limits?

A: There are three different groups affected.

Recipient Limit - All individuals - no more than 500 unique email addresses in the To, Cc, and Bcc fields combined. This can be increased to a maximum of 1,000 unique email address per request.
Recipient Send Rate Limit - Faculty & Staff = you can send email to 500 unique recipients per hour and a maximum of 2,500 emails per day.
Recipient Send Rate Limit - Students = you can send email to 250 unique recipients per hour and a maximum of 1,000 emails per day.

Q: Why are these limits in place?

A: The limits are in place to reduce the spread of phishing emails or further credential harvesting activities.

Q: What happens if the limits are exceeded?

A: Email delivery will fail.

You will receive an email with an error message of "Sending email address not recognized as a valid sender" or "550.5.1.8 Access denied, bad outbound sender".
Information Services will be alerted to this event and will contact you immediately as your account will be restricted from sending any further email.

Q: What if I regularly need to send mass emails?

A: There are 3 different options for sending mass emails.

Use Managed Distribution Lists - Open a Technology Support Request and Information Services can assist with creating dynamically populated lists based on department, school, or other specific criteria.
Use a Shared Departmental Mailbox - Open a Technology Support Request and Information Services can create a Shared Mailbox with a unique Email Address Identity for your team or department.
Send email via Delivra (not your Microsoft 365 Mailbox) - Delivra is our official mass email platform that is supported by Quinnipiac's Marketing and Communication department. There are no recipient rate limit restrictions and it is possible to send beyond our recipient rate limits noted above.