persist to-field #355

Xcode test results

Total	Passed	Failed	Skipped	Expected Failure	⏱️ Time
22	22	0	0	0	0.01s

Test	Total
IntegrationHooks	1	1	0	0	0
MTBBlockedMessageTest	21	21	0	0	0

All tests passed 🎉

				⏱️
1 (100%)	0 (0%)	0 (0%)	0 (0%)	0.00s

	`testRequiredFrameworksExist`

				⏱️
21 (100%)	0 (0%)	0 (0%)	0 (0%)	0.00s

	`test1pxBorder`
	`test2x2TrackerVendor`
	`testAdobe`
	`testBase64Email`
	`testCleanHtml`
	`testCSSTracker`
	`testDropboxHyperlinks`
	`testEscalentBackgroundCSSAndImgTagTrackers`
	`testGenericPixel`
	`testGoogleAnalytics`
	`testMailgun`
	`testMultipleBackgroundCSSAndImgTagTrackers`
	`testMultipleGenericPixels`
	`testMultipleNamedTrackers`
	`testRFC2392EmbeddedSpacer`
	`testSendgrid`
	`testSendy`
	`testSES`
	`testSpacers`
	`testTwoTrackersSameVendor`
	`testWhatCounts`