[amaurymartiny]

I built a tool to check if an email exists without sending any email. I also created a SaaS out of it: [link redacted].

The tool connects to the target email's SMTP server, and parses the response of the "RCPT TO" command. To avoid IP blacklisting, I use Tor.

The code is in Rust, 100% open-source. The core library is here: [link redacted]

[vincent_s]

Hah, I did something very similar with MailExists [1], but not Open Source and using expensive proxies instead of TOR ;-)

[1] https://www.mailexists.com/

[jtokoph]

Aren’t Tor exit nodes mostly blocked already?

[amaurymartiny]

> mostly

Using Tor, I can verify around ~60% of emails. Notably, the exit nodes can connect to Gmail/GSuite servers. So it's not that bad.

If Tor's exit nodes are blocked by a server, I fallback to Heroku, where I have right now 3 fixed-IP instances. And if I see that one of these also gets blacklisted, I would have it self-destruct and relaunch, Heroku assigns a new IP on each new instance.

[acid303]

Does Heroku reuse these IP addresses? Can someone get them after you?

[amaurymartiny]

I unfortunately don't know the answer to these two questions.