When can you send a Telegram message via NisWire?

  1. If you have the contact’s Telegram username
    Yes, you can always send a message.
  2. If you only have the contact’s Telegram number. 
    You can send a message if,
    - they have a "username" set for their profile, 
    OR
    - their "Who can send me a message" is set to "Everyone",
    OR
    - their “Who can send me a message” is set to “My Contacts” and your Telegram number is in their contact list.