Emails not working

Emails not working

I recently started using Zoho for my emails because my web host no longer includes emails in their service. all went ok until I wanted my website to confirm incoming orders to the customer and myself. It just refuses to do so and I have tried various different ports IE: 25, 465,587 etc it seems that zoho are blocking these. The platform we are using is sellerdeck (Actinic) It was working fine up until the day we had to switch to Zoho.
Is this a common problem , and is there some other port I can use. Any advise would be welcomed.