Hey @efedorenko, this library is no longer maintained (love postmark btw, heard good things even thought we use another provider.)

I rewrote it entirely and update it for 2022 and onward: https://github.com/ZooTools/email-spell-checker

• 💙 Written in TypeScript and removed jQuery
• ✅ Fixed a couple of bugs like this or this
• 🚀 Reduced bundle size to <2KB.

• ✨ Update TLDs (69+) and added modern startup domains (like .io, .so, .xyz or .dev)
• 🙏 Implemented suggestions that people made in this repo that were ignored.

Link: https://github.com/ZooTools/email-spell-checker

Come check it out and give it a ⭐️ for the effort.