I am a PhD student. Since a long time I did not email my supervisor. Thus, I want to text him but I did not know which email that should be written in the title.
Title your email something descriptive in a short statement.
Do not use "News" - what is news? You might be sharing your opinion about the media. You might be sharing an article you read about fashionable hats in the news. You might be sharing an engagement, marriage, childbirth, divorce, serious illness, change in the succession order of the British monarchy, taking a new job, winning the championship in your bar league basket weaving division. The title "news" says almost nothing - not about urgency or content or valence.
If you're sharing the latest results on some project you're working on, why not say that? "Updates on basket weaving data collection". Even better, don't bury the lede: "Basket weaving data collection now 50% complete". The appropriate title should depend on what you are sharing, there's no way anyone else can title your email for you in a meaningful way.
On the other hand, don't overthink it or spend time on making the title perfect or memorable - just frame in a few words what you are going to share.