@s7robin – I think it’s a coincidence. I’m using CF7 on many sites that have updated to WP 4.4.1 without problems.
I’ve now answered variations on the email sending question well over a 1000 times in this forum. Nearly every time we have an update to WP or CF7 we get a number of posts from people saying it’s due to the recent update.
I guess it’s human nature for people to associate the two events. With millions of people using CF7 every day, it’s inevitable that several hundred people have email sending problems each day.
When people come to this forum, when having problems after an update, and see someone else having a problem they sometimes conclude that the problem is the update.
That has never been true since I started answering this question a few years ago. Usually, after about a week, people stop associating the problem with the update and go back to finding the actual cause of the problem in their particular case.