A partial BODY.PEEK[n] fetch omits the section's MIME headers, so enough_mail's decodeContentBinary() has no Content-Transfer-Encoding and returns the raw base64 string instead of the decoded bytes. Fetching BODY.PEEK[] gives enough_mail the full MIME structure and getPart(fetchPartId) correctly decodes the attachment. Also adds an integration test that creates an email with a binary attachment, syncs it, and asserts the downloaded bytes match the original — this test failed before the fix. Closes #70 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>