we and our recipients receive fake mails from fake domains have names same with our mails with small different in spilling .

what was happened and how can we solve it ?

we and our recipients receive fake mails from fake domains have names same with our mails with small different in spilling .

what was happened and how can we solve it ?

 What are you using for anti-spam and anti-malware?

try and verify if your exchange is not exposed to open relay and get header of few such fake emails and then have the fake domain and IP blocked on gateways / edge itself .

Hi,

From your description, I recommend you enable anti-spam functionality on Mailbox servers. In Exchange Server 2013, the Content Filter agent, Sender ID agent and Sender Filter agent are available in the Transport service on Mailbox servers, but they are not installed by default.

For more information, here is an article for your reference:

Enable anti-spam functionality on Mailbox servers

https://technet.microsoft.com/en-us/library/bb201691(v=exchg.150).aspx

Hope this can be helpful to you.

Best regards,