Speed of email fetch

Speed of email fetch

Does anyone have any input on how to get the zoho email fetch rate to be faster??
We have had Zoho for over two years now and I have had it with our slow Zoho email fetch rate.  If I watch how long it takes for email to hit my zoho vs. my gmail account it can be up to 10 minutes later.  Our customers are always sending us files during phone conversations that they want us to look at. We cannot rely on Zoho for this important element in our sales cycle.  If I cannot get meaningful improvement on this by the end of the week I am cancelling all of our zoho subscriptions and making the switch. As big of a hassle as this might be it is unavoidable.