The version 400 was allmost ok ... well... allmost... NOT perfect...

But when I upgrade from 400 to 900 it becomes a disaster...

I set it to send

first day 3 messages, at 3 different hours, from 3 users  (each hour with his own user)

It was a total disaster:

First hour first user was send ALL 3 messages

Second Hour Second user send ALL 3 messages

Third hour Third user send ALL 3 messages...

Tested on all 3 sites .. same result...

I try to contact Sergey... Nothing ... no response...

So I switch back on older version 400..

Which are not perfect as I say... I receive some complains from real users that different users send same message... 

I advise Sergey to create a posibilities and add this option:

Chose exactly What user send what message at what time... so make it simple:

Time to send/Mesage to be sended/sender/

Sorry for the bad review but after upgrade to 900 on one site with fully trust in Sergey skills and NOT verify what was happening... I spend 3 day's to delete the wrong messages from conversation_table in mysql... 

Also a lot of users has lost credibility in one of my site after receiving all message from one user and again all message from other users...

(before upgrade I have set up 40 messages/40 users/40 day's)