Hi. I am e-mailed frequently by colleagues and customers in other countries and quite often they put an exclamation mark after my name i.e. Hello Leigh!
I have tried to find out why but have drawn a blank. Does anyone here know?

Hi Leigh

An exclamation mark is just used for excitement or surprise.

There is more on using commas, colons, and exclamation marks at the start of letters here.

I understand that, but why use it if you are querying an invoice?