Encrypted mails via SMTP / nodemailer

My YunoHost server

Hardware: VPS bought online
YunoHost version: 11.0.9.14
I have access to my server : Through SSH | through the webadmin
Are you in a special context or did you perform some particular tweaking on your YunoHost instance ? : no

Description of my issue

Hi,

I want to be able sending encrypted messages, using SMTP and nodemailer and Rocket.Chat as well. I’m not completely sure, if I encountered a problem or if it’s supposed to be like this and there is no problem at all.

Anyway, when I try to set the “secure” option in nodemailer to “true” or try to use the option “connect with TLS/SSL” in Rocket.Chat. In both cases I get the following error message (when trying to send an email):

[Error: 139889157539712:error:1408F10B:SSL routines:ssl3_get_record:wrong version number:../deps/openssl/openssl/ssl/record/ssl3_record.c:332:
] {
  library: 'SSL routines',
  function: 'ssl3_get_record',
  reason: 'wrong version number',
  code: 'ESOCKET',
  command: 'CONN'
}

Now I’m confused. When I don’t set the secure option in nodemailer to true, when I don’t connect via TLS/SSL, am I nonetheless sending encrypted mails via SMTP from my yunohost-server – or are my mails or any crucial connection unencrypted?

Thanks a lot for helping me understand this!

Best Valentin