Can activation server handle offline computers?

Actually, yes. Via the offline registration form. At https://yourdomain.jandrozd.eu/OfflineActivation/ resides the form you can send to customer. It works this way:

1. Customer installs your software and gets offline computer hardware ID.
2. From different online computer he/she visits offline registration form and enters e-mail, serial and offline computer hardware ID.
3. License generated automatically and sent to e-mail as file.
4. Customer can bring license file on USB drive and load it on offline computer.