Receiving emails have been "spotty"

Receiving emails have been "spotty"

So we have just recently transitioned to Zoho. We noticed that when weswitched we began randomly having issues with people sending mail to us.It seems some are coming through but others at times are not. To add,these are people that have had our email "auto complete" savedin their contacts for years. Since we've transitioned to Zohowe've notice this emerge. Ironic? Or is this an issue anyone isaware of?