not receiving emails from team member with same domain

[DDiedrich]

I am not receiving emails from my co-worker with the same domain.

[DDiedrich]

All 6 of my co-workers are not able to receive emails from 1 with the same domain.  Anyone have any ideas about why this is happening or how to fix?

[JohnDoh]

Roundcube is a mail client. A free piece of software your email provider is using to give you webmail access. Your email providers mail server is responsible for sending/receiving email. Please contact your email provider for support.