SCOM alert email notification delays

Hi All,

We are seeing 10 hours delay in alert email from SCOM.

so far tested  the exchange server reachability, ping ,tracert etc.
Also sent couple of test emails. No issue at all. 

Only SCOM alert emails are seeing huge delays. we are receiving notification in the evening about alert generated in the morning .
Cycled scom and sql services. renamed healthstate folder as well.

Any pointers what else to troubleshoot.?

Manish