[otrs] Delay before sending e-mail

Hello, Everyone! I've installed OTRS on a Debian-based Linux Distro and, fortunately, everythings goes okay (so far), except for a delay I get when performing an operation which relies on e-mail sending functionality, like answering a customer ticket. I run it on a MS Exchange Server, in an intranet. I think OTRS might be performing some kind of checking before actually sending the mail. If that's the case, what would that be? Have you ever experienced that? Best regards, Harry