Yes, it is possible to send notes to users who are offline using Notezilla . This is done via the cloud account. Notezilla 's cloud feature lets you sync your notes with any device and also send notes to users who are offline.
For this, the sender & recipient would need to create cloud account. Right click on Notezilla icon and choose Sync option and create Notezilla.Net account. Once the accounts are created on each computer, you can go to the sticky note and choose Send To->Contact option to send the note to that contact. The recipient will receive the note when she switches on her computer. Since the notes sync with the cloud, one can access notes from any device, Android or iPhone.
Please watch this short video for clarity: