Bounce falls into the main box. Why?

@ltdviso - Can you please tell me what system mailer are you using from backend > settings > common ?
Problem is that if you are using PHPMailer, then phpMailer is not settings a return path anymore, it's their design decision, so basically they will not et your bounce address to have the emails return to it, but they will use the from address, so the solution is to use swiftmailer instead.
yes, you are right, I noticed this when I switched to php - so I thought I would go faster (I have an eternal war with dosage and speed). Thank you for your prompt response
PHPmailer does the right thing: to not set the ReturnPath, since it is the last servers' job to set the ReturnPath.
This is, so that these receiving servers can cope with many mail scenarios (incl purposefully wrongly set headers, e.g. ReplyTo/ReturnPath or correctly setup and operated mailing lists), and hence they will reply to whatever works, mostly FROM, but also other addresses in the header or at the servers involved in sending (whole infrastructure).
See here: RFC5321, p57:

And that makes it clear, that the so called 'compliant' SwiftMailer is actually misleadingly setting the ReturnPath, when it should not. Maybe SwiftMailer should be removed from MailWizz?!

we also notice that 90% of answering machines started to bounce for a while (very long ago when I bought it) and also 1/2% of real answers. We basically do not pay attention to this.
I can say one answers from real users come from specific mail systems or programs. (some kind of corporate systems - I can see it in the fonts and the style of the answer)