Encode non-ASCII SMTP attachment file names according to RFC 2231

[ashrafiucse]

Description

Upgrade javax.mail from the 2013 beta javax.mail:mail:1.5.0-b01 to com.sun.mail:javax.mail:1.6.2, so that attachment file names containing non-ASCII characters are encoded according to RFC 2231.

The javax.mail.* namespace is unchanged, so no code changes are required. The dependency verification metadata already trusts the com.sun.mail group (PGP key 4F7E32D440EF90A83011A8FC6425559C47CC79C4), so no verification-metadata.xml changes were needed.

Motivation and Context

Fixes #6652

The SMTP Sampler mangles attachment file names that contain non-ASCII characters. Sending an attachment named текст.txt produces:

Content-Type: text/plain; charset=us-ascii;
        name="B5:AB-attachment....txt"
Content-Disposition: attachment;
        filename="B5:AB-attachment....txt"

so recipients see garbage instead of the original file name.

Root cause: SendMailCommand builds attachments with MimeBodyPart.setFileName(String). The old javax.mail:mail:1.5.0-b01 does not encode non-ASCII file name parameters according to RFC 2231.

As suggested by @FSchumacher on the issue, upgrading to 1.6.2 fixes the encoding. With this change the same attachment is now sent as:

Content-Type: text/plain; charset=us-ascii;
        name*=UTF-8''%D1%82%D0%B5%D0%BA%D1%81%D1%82.txt
Content-Disposition: attachment;
        filename*=UTF-8''%D1%82%D0%B5%D0%BA%D1%81%D1%82.txt

How Has This Been Tested?

• New SendMailCommandTest:
  • testNonAsciiAttachmentFileNameIsEncodedPerRfc2231: builds a message (via prepareMessage(), no SMTP server needed) with an attachment named текст.txt and asserts the raw message contains filename*=UTF-8''%D1%82%D0%B5%D0%BA%D1%81%D1%82.txt and no mangled name
  • testAsciiAttachmentFileNameIsNotEncoded: asserts pure ASCII names are still emitted as plain filename=attachment.txt (no RFC 2231 encoding)
• Full :src:protocol:mail:test (4 tests) and :src:components:test (549 tests, MailReaderSampler shares the dependency) suites pass
• ./gradlew classes style passes
• Verified the original repro end-to-end against a locally built distribution

Screenshots (if appropriate):

Not applicable (raw SMTP headers shown above).

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly. (release notes entry added to xdocs/changes.xml)