Troubleshooting the 'Collection size exceeds maximum size of 1,000' error

Solution 1: Restrict Event Ownership

1. Navigate to each User record for the people who can own events and click the box for 'Can Own Events'.

Note: This field may need to be added to the page layout.

2. Navigate to Setup and search for Custom Settings.
3. Click Manage next to Event Settings.
4. Select Edit.
5. Check the box for Restrict Event Ownership. If checked, only users with "Can Own Events" profile setting can be set as the Event Owner.
6. Save your changes.

Solution 2: Remove unused templates from the folder

You might also hit this error if you have over 1,000 email templates in the Event Email Template folder. In this case, you should remove unused templates from the folder.

You can either move unused templates to a different folder:

1. Navigate to the Campaign Builder tab.
2. Select the Templates icon in the bottom navigation bar.
3. ​In the Templates List window, select to Edit your email template.
4. Click the Template tab and change the Folder.
5. Save your changes.

OR

Delete email templates that are no longer used:

1. Navigate to the Campaign Builder tab.
2. Select the Templates icon in the bottom navigation bar.
3. ​In the Templates List window, select the Delete icon.