Hostname validation for certificates should be enabled by default

JavaMail 1.0 specifications has hostname validation of certificates disabled by default [1]. This is a very insecure default configuration, and opposite to what would be expected as a default.

As part of Jakarta Mail 2.0 this should be changed to be secure by default.

[1] mail.smtp.ssl.checkserveridentity defaults to false

Start by reviewing the Jakarta Mail 2.0 specification and the mail.smtp.ssl.checkserveridentity property, whose default is currently false. Trace where this default is defined and identify the specification or compatibility tests that cover it. Done means hostname certificate validation is enabled by default and the documented behavior is consistent.

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