When you want to praise a colleague or employee then you should do it in person, but if you have something negative to say then it should be done via e-mail, phone or text.

Whenever possible, communication should be done in person. When "in person" isn't possible (thanks covid) then aim for a video meeting. When you are praising someone, they will feel it more when they can look at your face as you are saying it. It allows you to build your relationship more quickly and easily. When giving negative feedback, this allows you to draw from your relationship and also your body language so that the other person understands that although something should have been handled differently, everything will be ok. You should remain calm and use a soft voice to communicate that you are still on their team, but they need to do things a bit differently to make things work better.