JavaMail and Oauth2: Exception "Can't send command to SMTP host" / "SSLHandshakeException: No appropriate protocol" - oauth-2.0

Question

I get the following exception when trying to send a mail with JavaMail with OAuth2:
javax.mail.MessagingException: Can't send command to SMTP host (javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate))
I have already checked dozens of stackOverFlow posts and none of the solutions work.
This is my javamail config (commented out some other configs I have tried):
...
String oauth2_access_token = <procedure to aquire a token>;
Properties props = new Properties();
props.put("mail.host",config.getString("MAILSERVER"));
props.put("mail.smtp.port", config.getString("MAILPORT"));
props.put("mail.smtp.auth", "true");
props.put("mail.transport.protocol", "smtp");
props.put("mail.smtp.starttls.enable", "true");
props.put("mail.smtp.starttls.required", "true");
props.put("mail.smtp.ssl.protocols", "TLSv1.1 TLSv1.2 TLSv1.3");
//props.put("mail.smtp.ssl.trust", "*");
props.put("mail.smtp.auth.mechanisms", "XOAUTH2");
//props.put("mail.smtp.auth.xoauth2.disable", false);
//props.put("mail.smtp.sasl.enable", "true");
//props.put("mail.smtp.auth.login.disable","true");
//props.put("mail.smtp.auth.plain.disable","true");
props.put("mail.debug", "true");
props.put("mail.debug.auth", "true");
// Connect
javax.mail.Session mailSession = javax.mail.Session.getInstance(props);
mailSession.setDebug(true);
SMTPTransport transport = (SMTPTransport) mailSession.getTransport("smtp");
transport.connect(config.getString("MAILSERVER"),
Integer.parseInt(config.getString("MAILPORT")), config.getString("MAILUSER"), oauth2_access_token);
Here is some output:
[apache-tomcat-9.0.54]: DEBUG SMTP: useEhlo true, useAuth false
DEBUG SMTP: trying to connect to host "smtp.office365.com", port 587, isSSL false
[apache-tomcat-9.0.54]: 220 SOMEANONYMIZEDSERVERPREFIX.outlook.office365.com Microsoft ESMTP MAIL Service ready at Wed, 16 Mar 2022 10:16:37 +0000
DEBUG SMTP: connected to host "smtp.office365.com", port: 587
[apache-tomcat-9.0.54]: EHLO MY_COMPUTER_NAME
[apache-tomcat-9.0.54]: 250-SOMEANONYMIZEDSERVERPREFIX.outlook.office365.com Hello [MY_IP_ADRESS]
250-SIZE 157286400
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-8BITMIME
250-BINARYMIME
250-CHUNKING
250 SMTPUTF8
STARTTLS
[apache-tomcat-9.0.54]: 220 2.0.0 SMTP server ready
[apache-tomcat-9.0.54]: EHLO MY_COMPUTER_NAME
[apache-tomcat-9.0.54]: ERROR 2022-03-16 11:16:39,407 [..MyProgramException..] - javax.mail.MessagingException: Can't send command to SMTP host (javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate))
I think it has to do with issuing the AUTH command because it is not listed in output. The connection over TLS is established successfully so I think the SSLHandshake Exception might be misleading. So what gives?
Might it have to do with the token? The scope I had to use for the token aquisition is ".default". "Mail.Send" didn't work.
I am using the newest JavaMail version 1.6.2 and AdoptOpenJdk 11.0.12.
I also double checked java.security config. TLS 1v2 and 1v3 algorithms are not disabled.

Answer 1

I found the solution myself. Maybe somone can make use of it:
The code above was not false to my knowledge. The actual reason was, that I should not have used a token acquisition with client credentials but only with username/password and client id.
I am not sure if JavaMail supports this because in the documentation I could not find anything about it. The rare examples about this are usually with client credentials.
As you can see above, no AUTH command was triggered because I had not the permission to do it obviously.
What I needed to do aswell was to use the Microsoft Graph API not only to aquire a token via "password/username provider" (this type) instead of the "client credential provider" (link) but also to actually trigger a send mail command via Microsoft Graph API (link).
The client credential provider was in my case not sufficient because the admin had not specified permissions to send mails.
Thus, I didn't use JavaMail anymore for this and needed another token acquisition provider.