Finding a reliable Mass DM provider right now is incredibly tough because Discord's automated intent detection and token-burn rates are at an all-time high. Most public services you find on Telegram are just exit scams or re-selling dead scripts.
If you want this done right, don't buy "service packages." Instead, look for a reputable vendor selling access to self-hosted multi-threaded infrastructure.
By running your own tool, you can pair it with residential or mobile proxies, use an external automated captcha solver, and manage your own token pools. It requires more backend work on your end, but it is the only way to successfully scale a mass campaign without your provider vanishing with your money mid-run.