Your sales channel likely sends emails on your behalf when orders are marked shipped by SKULabs. When that is not the case, you can enable email notification using your store settings under "Shipping defaults and settings" using an option called "Shipment notification email".
After you've enabled email notifications, if you're still experiencing issues, rest assured that SKULabs utilizes a transactional email service with very high deliverability statistics meaning it is incredibly rare that the email was mis-delivered so long as the email address is correct.
The best way to diagnose shipment notification email issues is to open up an in-app conversation system window (the orange icon) and include an email address and order number affected.
Most of the time, the customer has simply lost the email in their inboxes. We have no reported issues with emails being sent to Spam on a regular basis due to the quality of the email service we use. If you are experiencing reports of tracking emails going to spam, we recommend you review your shipment notification template for common pitfalls when writing highly-deliverable emails.