Need to include every student in an email.
You've got two options:
Hi MARTHE VAN GORDER and welcome to the Community! Are you referring to messages in the Inbox/Conversations (see How do I use the Inbox as an instructor?)? If so then when you compose a message and select the course attendees from the "search by user" field (see link above), then you should be able to hit "CTRL" and select as many of the students as you like. If you want to just pick everyone then if you click on the little yellow arrow next to "students" in the search by user field, then an option should appear to send the message to all students (see below):
It is worth noting that the Inbox is not a traditional email system. Messages are designed to be sent to individuals sharing a class together so if you don't have a student in one of your classes at this time, they will not appear as an option in the Inbox. In addition, messages are not sent to participants if the class has not been published (the same holds for course announcements). Often institutions set up Canvas so that inbox messages are forwarded to the institutions traditional email service, but this is probably not always the case.
I hope this helps!
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