I use the LLDAP application (`https://github.com/lldap/lldap`).
I want to set up an SMTP server to send password reset links. I have an MX PLAN 5 with OVH. I get the following error message when I send an email : `Connection error: Connection error: received fatal alert: ProtocolVersion`
The application can send emails with other SMTP servers (tested with gmail). I also have other applications that work well with OVH's SMTP servers. I tested with TLS (465/tcp) and STARTTLS (587/tcp) both do not work.
Thank you for your help!
28521 
16.03.2023 11:28
Hello,
There is a good article here: https://mailtrap.io/blog/starttls-ssl-tls/
Is there a debug mode in your library, allowing to show whether the negotiation fails in the TLS version (e.g. TLS 1.1, 1.2 or 1.3) ? or at a later step when both parties have to agree on a common crypto engine to use ?
ssl0.ovh.net provides service on both ports 465 and 587, but they are not interchangeable. On port 587 the dialog begins in plaintext and the client (your app) must sent a STARTTLS command. This is part of the protocol.
Try using TLS with port 465 and check your SSL/TLS version.
Quick addition on my previous post:
OVH has removed support for the deprecated TLS1.0 and TLS1.1
So, please ensure that your application implements at least TLS1.2.