What thresholds/limits are in place?

  • You should not send more than 1000 emails in a 24-hour period.
  • Emails are sent at a maximum rate of 30 emails per minute (users using a modern mail client like Outlook won't notice this as the mail client will retry the messages automatically). 

  • Each email should have no more than 150 recipients per message.
  • If your needs exceed this, you should look at using a mailman list or using an application which can send out your email in a metered fashion (e.g., GroupMail).

Why are these limits in place?

  • Increasingly, compromised account credentials have been used by spammers to send their email via UWaterloo email systems.
  • To preserve our reputation with other service providers (e.g., Gmail, Hotmail, Yahoo, Rogers).
  • Mass mailing is what spammers do. You need to ensure that your email does not look like spam. These limits actually help to ensure that your email is delivered.

What happens if I send more than the suggested limit?

  • Servers receiving email for delivery will apply their own policies. These policies vary from server to server and company to company.
  • In some cases, the server will refuse to accept further email after a certain limit has been reached.
  • In other cases they will accept the email but at a much slower rate.
  • In both cases, your email can create a backlog of other messages destined for the same company or institution, which will negatively impact others at the University of Waterloo.

Other resources:

Mass email and anti-spam law and guidelines

Faculty and staff mass email guidelines (University Communications website)

Blast email request and procedures (Registrars' website - authentication required)

Mass email tools

Mailing lists using mailman (PDF) (CAS authentication required)