- Validate all recipients with net/mail.ParseAddress; reject CR/LF.
- RFC 2047 (Q-encoding) for Subject and FromName so CRLF and non-ASCII
cannot break out of headers.
- Honor use_tls: implicit TLS on port 465 with certificate verification;
otherwise document the opportunistic-STARTTLS path.
- Table-driven tests for validation, injection neutralization, and
multipart building.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
igodwin
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