Is a comma necessary?

[Kohyoongliat]

Hello everyone!

Is a comma after “Hello” necessary? And is the exclamation mark after “Thanks” the correct punctuation?

Thanks!

[Anglophile]

I’d say, it is necessary because you are seeking someone’s attention by the interjectory ‘Hello’ and then mentioning the name individual or collective.
The exclamatory mark is not necessary. However, nowadays, it is also found used to highlight or close a wish, a curse or an important/appreciative/notable remark, which I follow suit!