How do I send a bulk message on Telegram?
I just found a software called TexSender that is able to send bulk message on Telegram. It is very simple to use and it allows to send message also to contacts not saved in your address book or in Telegram contacts. Once the program is open, you need first to click on Start Service and login to your telegram account (from google chrome browser). Then access to the module “Send to Usernames” or “Send to Phone Numbers” to import the list of usernames or phone numbers, enter the message and click on Start button.
All messages will be sent automatically to all imported users. At the end you can click on “report” link to see the details of the campaign.
This software does not use API, it is a powerful tool that automate the manual operations to make a multiple sending of your message. This reduces the risk of your account being suspended, but it's still a good idea to set a delay between bulk message so you don't look like a spam submission.