We have suddenly today started getting delayed delivery notifications through our Outlook mail clients but have not touched any settings so wondered where the problem may lie?

We use Zoho Mail as our mail host which is then connected through a POPcon application to a Small Business Exchange server and then on to our outlook mail clients on the local terminals.

We are not seeing any of the sent items on Zoho Mail either which is strange as all items prior to today were delivering with no issues but not transfering to our Zoho Mail sent items.

Any suggestions on the reasons the mails are being delayed?