The majority of the withheld messages were deemed "pesonal" or withheld for other reasons, according to York. 

Also notable, according to York, is that the 50,000 Strzok-Page texts only include messages sent and received on FBI-issued Samsung phones - despite several text messages which make clear that the two agents also discussed their politically tainted investigations over their personal iPhones using iMessage. 

For investigators, those are particularly intriguing texts – what was so sensitive that they couldn't discuss on their work phones? – but the number of those texts is unknown. And of course, they have not been turned over to Congress. -Washington Examiner