In Odoo 10:

I have configured Outgoing Server, which works perfectly, however what concerns is the time it takes to deliver the mail to official user. (or Non-Gmail Addresses)

Lets say I have configured Outgoing servers using my corporate credentials, i.e smtp.xxx_domain.com

Now am trying to send an email from Odoo to the partners, one having Gmail address, while other having address user@xxx_domain.com.

Now the mail received in the Gmail Account is pretty faster, almost immediate, however the other user receives mail into his Outlook/Webmail after god-damn delay.

Which seems fishy, So I wanted to know, how to overcome this. Because not all of our customers uses Gmail account, so its pretty time-consuming to wait for mails, which is delayed due to the above cause.