digest-md5 | The Digest : :MD5 Perl module

You can try with defining module as :

When calculating the response, the third line concatenates the buffer y (which contains an MD5 hash) with strings, whereby y is implicitly converted to a string using UTF-8.
However, an arbitrary byte sequence, such as a hash, will be corrupted by a UTF8 encoding, s. here. To prevent this, the individual parts should be concatenated as buffers rather than strings.
In contrast, the remaining concatenations (in this and the other lines) are not critical, since they are true strings:

I checked your setting and it works for me.

But my debug output looks different after the Server host key

RFC4954 provides two examples fo the AUTH PLAIN SMTP authentication mechanism. The first is like you're seeing:

First I have to give credit to @Robert who answered my first question in his comment, and in his comment regarding my second question he mentioned DKIM, which put me on the path to solving my second question.

So the answer to my first question is everything is encrypted in the jakarta mail example, including the login and the message. You don't need to use the smpt servers public key because in my case it uses a certificate signed by a commercial Certificate Authority. (per @Robert and https://stackoverflow.com/a/16843712)

As for my second question, why is goole marking my emails as unverified when they are received, the answer is to sign the emails using DKIM when sending them. To do this I followed these steps:

To sign my emails I used this library: https://github.com/markenwerk/java-utils-mail-dkim. Note I had to revert to using javax mail from jakarta mail because this method in the library expects a javax.mail.internet.MimeMessage DkimMessage(mimeMessage, dkimSigner);

I then used this tool to produce the private and public keys: https://tools.socketlabs.com/dkim/generator Paste the private key into a file and name it with the .pem extension.

Now you have to add a DKIM TXT record to you websites DNS settings. Here is a link which explains how: https://blog.mailtrap.io/create-dkim-tutorial/

The library expects a .der file so convert the .pem to .der using openssl, with this command: openssl pkcs8 -topk8 -nocrypt -in myDkim.pem -out myDkim.der -outform der

I then used the following method to sign my emails, adapted from the instructions on the librarys web page.

It's a login/sender related issue.

554 5.2.0 SendAsDenied

You are trying to send a mail with a sender different from your outlook login address.

In your case, your login is one and the MAILFROM you're trying to send is a different one:

MAIL FROM--> dell@dell-Precision-M6400

LOGIN --> myMail@outlook.com

So SendAs(dell@dell-Precision-M6400)Denied is thrown.

To make a simple test, try sending the same message but with your outlook credentials set as MAILFROM. It should work without errors.

In order to set different valid senders, add the new sender in the outlook admin panel. That would avoid the exception if trying to send the email with a different sender than your login.

You can find a sample code which generates the masked password in the Jboss' developer blog: https://developer.jboss.org/people/aabdelsa/blog/2019/09/05/support-for-masked-passwords-in-the-client-xml-configuration Hope it helps