i sent someone an e-mail telling him that i was sorry because i couldn't come to the meeting since i had a problem with my car
this was his reply:
As long as you are all safe, sound and producing units
what does this mean?
"Safe and sound" means you haven't been injured; you are alright.
(It sounds like this email is not from an English native).
I don't know what he means by "producing units", though the context suggests that he is your boss, and that "producing units" is something you do for work, and he's glad you are still able to do it.
If that doesn't make sense, you might have to write back to him and ask what he meant.