Customizing the email notifications sent to accounts when they reach hosting limits will depend on the specific hosting control panel or software you are using. I'll provide general steps for a few popular control panels:

cPanel:

1. Log in to WHM (Web Host Manager) as the root user.
2. Navigate to "Server Configuration" > "Tweak Settings."
3. Click on the "Mail" tab.
4. Locate the option labeled "The system will send a notification to the user when their disk quota reaches this percentage."
5. Adjust the percentage value to control when notifications are sent.
6. Save the changes.

To further customize the email template:

1. In WHM, go to "Home" > "Service Configuration" > "Exim Configuration Manager."
2. Under the "Basic Editor" section, locate the "Message Text" field.
3. Customize the email template to your preference, including the message subject, body, and any placeholders for dynamic content.
4. Save the changes.

Plesk:

1. Log in to Plesk as an administrator.
2. Go to "Tools & Settings" > "Notifications."
3. Find the notification event related to resource usage limits (e.g., "Resource usage limits exceeded").
4. Click on the event to edit its settings.
5. Customize the email template, including the subject and message body.
6. Save the changes.

DirectAdmin:

1. Log in to DirectAdmin as the administrator.
2. Navigate to "Admin Level" > "Admin Settings."
3. Scroll down to "E-Mail Options."
4. Find the option labeled "When a user is over quota."
5. Customize the email template, including the subject and message body.
6. Save the changes.

Other Control Panels:

For control panels not mentioned here, the process may vary. Generally, look for settings related to email notifications or alerts. You may also want to consult the control panel's documentation or community forums for specific instructions.

Remember to test the customized notification to ensure it appears as expected. Always keep backups of any template changes in case you need to revert to the default settings.