shouldFail: true,
		},
	}

	// Validate if the extracting headers.
	for i, testCase := range testCases {
		metadata := make(map[string]string)
		err := extractMetadataFromMime(t.Context(), textproto.MIMEHeader(testCase.header), metadata)
		if err != nil && !testCase.shouldFail {
			t.Fatalf("Test %d failed to extract metadata: %v", i+1, err)
		}
		if err == nil && testCase.shouldFail {