sharepoint online workflow suspended

I had the same issue and I was able to resolve it by using app step.

Please Note you can get this error if UPS is not configured. Also if Email addresses does not belongs to the farm domain.

Please Add your Send Email action in APP Step. If you do not know what is App step. Just a quick steps.

https://msdn.microsoft.com/en-us/library/office/jj822159.aspx?f=255&MSPPError=-2147217396