Getting unknown mail on all mail id's

Dear Support,

We are getting some malicious mails & getting mail from our domain also. Please get this checked asap.

Example -

accountsmanager nbsfrna375@nirmalbang.co.in
Hello,

** I would like to book : 3 bed with a rollaway room for 7 nights.**

** We are appreciate your immediate attention to this matter.**

accountsmanager
** e-Mail:accountsmanager@treehousehotels.in**

Please check ASAP.

Regards,
Himmat@treehousehotels.in