emails from my colleagues in the same domain go to Junk E-Mail

We have two email cloud services, one from Office 365 and other from another company.  The emails that my colleagues send to me or to other recipients in O365 from the OTHER cloud service goes directly to Junk E-Mail, causing confusion and the worst, comments that the junk email filter in O365 has something wrong.  The emails sent from O365 to the OTHER cloud service, are received correctly.

Thanks in advance.