As soon as you complete the label purchasing process, all recipient email addresses that you've included in the shipment's information will receive an automated email notification alerting them that they have a package coming. That email will include their tracking number, along with a brief message to let them know that they won't see movement on that number until the package is tendered to USPS.
Once your packages are picked up by USPS (or dropped off at a USPS location), we'll notify them that the shipment is on its way and provide an estimated delivery date (if USPS gives us a date to share).
If the package enters an "exception" status indicating a possible problem with delivery, they'll receive a notification right away so they can review the issue and connect with you if an address correction is needed.
As the sender, you can always see up-to-date information about a package's transit status and tracking by going to "My Shiplane Orders" and clicking on the shipment batch to see details.