Loss of emails?

Loss of emails?

Hello

I've just moved our business of around 10 emails over to zoho and we're noticing that some emails around the office are getting lost.
Our domain : http://bradburyoutreach.com
All was fine up until today where emails have been arriving considerably late (1/2am in the morning when we close at 5pm) or not simply arriving at all.
I've checked spam, I've gone into control panel and looked for any emails that need retrying, but no emails were there.
Any help on this issue?