MimeBodyPart bp = new MimeBodyPart();
// no content-id
assertNull(bp.getContentId());
// normal case
final String cid1 = "cid.1@android.com";
bp.setHeader(MimeHeader.HEADER_CONTENT_ID, cid1);
assertEquals(cid1, bp.getContentId());
// surrounded by optional bracket
bp.setHeader(MimeHeader.HEADER_CONTENT_ID, "<" + cid1 + ">");
assertEquals(cid1, bp.getContentId());