delivery of messages from zoho mailbox are delayed

Dear Support team,

Delivery of my e-mails to mail server " adityabirla.com" are delayed. Sometimes it takes more than one hour to reach the destination. No spam / junk e-mail settings are set at receiver end. If I'm sending an e-mail from gmail account to same destination, it get's delivered instantly.

E-mail header of on of the messages sent out today with described issue:

Date: Mon, 30 Jun 2014 00:55:42 -0700
From: "balazs.czumbel" <balazs.czumbel@primeinfo.eu>
To: Lapohos <Eva.Lapohos@adityabirla.com>
Message-Id: <146ebc4c3a7.3020072223013116273.6803203821207514982@primeinfo.eu>
In-Reply-To: <CFA4F7E15F099D4AAAC09A6B0F0249CC21810907@c3cwymb02.columbianchemicals.com>
References: <CFA4F7E15F099D4AAAC09A6B0F0249CC21810907@c3cwymb02.columbianchemicals.com>
Subject: timesheet
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="----=_Part_386502_2121568890.1404114942018"
X-Priority: Medium
User-Agent: Zoho Mail
X-Mailer: Zoho Mail
X-ZohoMail-Sender: 198.160.102.41

I'm using the web client accessing my e-mail portal using following URL: https://mail.zoho.com/portal/primeinfo.

Please help to get fixed this issue a.s.a.p.

Thanks !

Kind Regards,

Balázs