Some email providers notify Groups.io when group messages end up in their (the provider’s) users’ spam folders. Most likely, the group messages were automatically flagged as spam by the email provider rather than having been specifically marked as spam by the users.

When Groups.io receives such a notification, the system automatically unsubscribes that member from the group. Groups.io also sends the member an email with a link that lets them automatically and quickly resubscribe to the group if the spam flagging was a mistake. The email lets the member know to check their spam folder and mark any messages in there from Groups.io as not spam, to help train the email provider’s spam filters to make fewer mistakes about Groups.io emails.

Group owners and moderators can check the activity log for members who were removed because group messages were reported as spam to their email providers:

1. Desktop browser: On your group’s left menu, select Admin > Activity.
   Mobile device: Tap the More icon at the bottom of a group page, then select Admin > Activity on the More menu.
   The Activity page is displayed.
2. (Optional) If you want to confine the search to a specific date or range of dates, select the applicable option from the Any Time list at the top of the page.
3. In the actions list, scroll down to and select Spam - System removed member due to spam report. A list of the members who were removed because of reported spam is displayed.

For additional information about this situation, see the wiki in the GroupManagersForum group.