Unable to send emails with postfix

[loxK]

I have an email server powered by postfix. My clients can connect using these settings :

• username: [email protected]

• port: 587

• security: STARTTLS

• OS: Ubuntu 22.04

So I have :

PDS_EMAIL_SMTP_URL= smtps://user%40domain.com:####@mail.domain.com:587/

When PDS send an email I have this error :

{"type":"Error","message":"181C3F0CD4700000:error:0A00010B:SSL routines:ssl3_get_record:wrong version number:../deps/openssl/openssl/ssl/record/ssl3_record.c:354:\n","stack":"Error: 181C3F0CD4700000:error:0A00010B:SSL routines:ssl3_get_record:wrong version number:../deps/openssl/openssl/ssl/record/ssl3_record.c:354:\n","library":"SSL routines","reason":"wrong version number","code":"ESOCKET","command":"CONN"},"msg":"unhandled exception in xrpc method com.atproto.server.requestPasswordReset"}

But I can connect to it with my clients (indeed) and OpenSSL :

# openssl s_client -starttls smtp -connect  mail.domain.com:587
[...]
---
SSL handshake has read 3397 bytes and written 428 bytes
Verification: OK
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 2048 bit
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)
---
[...]

What am I doing wrong ?