This article applies to Salesforce Classic and organizations that do not have the 'Enable User Control over Task Assignment Notifications' setting enabled via Setup, search Activity Settings in Quick Find.
If your organization has the 'Enable user control over task assignment notifications' feature enabled, see the Considerations for Enabling User Control of Task Notifications documentation for more details on how users can set reminder preferences individually in their My Settings: Update Your Personal Settings.
As per the Productivity Features: What’s Different or Not Available in Lightning Experience documentation, "Lightning Experience doesn’t display any options to send an email when you assign a task to someone." If you would like to see the ability to select 'Send Notification Email' added to Lightning Experience with a future release please consider promoting the Idea: Task Notification in Lightning.
For organizations without the 'Enable user control over task assignment notifications' enabled, users can set their default preference via the following steps:
1. Create or edit an existing Task record
2. Click the 'Send Notification Email' checkbox to either add or remove the check.
4. Check the 'Make this the default setting' checkbox
5. Click Save.
Notes: This default setting will apply to all Task creation/edit pages under all objects and related lists throughout the application. The setting can be changed the next time a non-default value is selected.
For example, if you selected "false" as the default, the next time you select "true" for the checkbox, the "make this default setting" option reappears so you can make the "true" value the default.
This setting takes precedence over the Email Notification Checkbox settings in the "Task Layout Properties" page: "Show on edit page" and "Select by default".
The only exception is on the "log a call" task page, where there are two "send notification email" check boxes. The "Make this the default setting." checkbox doesn't work on this page.
See Also:
Why is my "Send Notification" checkbox still missing or not available on the Task Page Layout
Change Default reminders for all users
Task Assignment notification emails are not sent to the owner of the task if they create the task themselves
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