Greeting-E-mail Writing

Asking the other's situation
How are you?
How are things going?
How is everything?
How's everything at your end?
What's new?
What's up?
What are you up to?
What have you been up to recently?
What's going on?
How's your school/university life going?
How did your exam(s) go?
I'm sure you did an excellent job.
I hope you had a pleasant / relaxing holiday.
I hope all is well with you and your family.

Describing one's situation
I'm doing all right/Okay/fine.
I'm doing very well.
I'm keeping very busy.
I'm keeping myself busy with my studies.
I'm keeping myself busy as usual.
Everything is okay/fine.
Everything is going very well.
Everything is pretty much the same as usual.
Not much is new here.

Describing one's health
I'm not feeling very well.
I think I need a few days off.
I really need some R&R(rest and relaxation)
I've caught a cold.
I have a sore throat.
I'm feeling nauseous today.
I think I have a slight fever.
I've been feeling under the weather all day.
I've been feeling lethargic lately.
I've been sick for over a week now.
I can barely get out of bed.
I have a pain in my chest/stomach/back/head/neck/throat.
I have a bit of a (an) headache/stomachache/earache/toothache.
I'm finally starting to get better.
I've regained my strength/energy.
I've gained/lost some weight.
I've lost over 5 pounds since getting sick.
I feel a whole lot better today.
I've never felt better.

e.g
Hi Tony,
How's your vacation going? You must be having an awesome time in Europe! Which countries have you visited so far? I got a part-time job as a waitress and I'm enjoying it so far. Anyway, we all miss you and can't wait to see you when you get back. Be sure to write soon.
Best wishes,
Daniel

Dear Jake,
I was so glad to receive your letter. It's been about two weeks since I was transferred to our southwestern branch. The office is a bit smaller and I'm still getting used to the new environment, but my colleagues are all very friendly. How's everything going at your end?
Warm regards,
Daniel