[otrs] Sending mail issue with Office365

Dear All, We are using OTRS in our company for supporting customers. Our office mail server is hosted with Microsoft Office 365. I have no problem to receive emails. But while sending email, it always go out from root@localhost instead of expected configured address. I have configured the SMTP setting in SysConfig -> Core::Sendmail. My configurations are as follows. SendmailModule SMTPLS. SendmailModule::Host smtp.office365.com. SendmailModule::Port 25. SendmailModule::AuthUser user@domain.com. SendmailModule::AuthPassword MyPassword. Because of this, the notifications are only sending to SPAM folder while system send it to office365 Domains. The OTRS version is 3.3.9. Kindly help to resolve this. Regards Nix STC