Hi! I ran into this problem. 
I am in doubt whether to use "We have just received" or "We just received". I'm not so good at English grammar.
Also (off topic) is it correct to say "Thanks very much for your message" or should I use "Many thanks for your message" instead?
Thanks in advance for your help!

I am in doubt whether to use "We have just received" or "We just received". I'm not so good at English grammar.
Also (off topic) is it correct to say "Thanks very much for your message" or should I use "Many thanks for your message" instead?
Thanks in advance for your help!
Comments
If this is a business communication, you might want to use the first form of the second case, changing 'thanks' to 'thank you'.
With a clear indication of the completed event, use past: 'I finished the work at 10 o'clock'.