Not able to send mails due to this error

I am creating and sending mails (set up on office 365) using exchange server. I am using EWS server in java to send mails. From a week ago, I am getting the below issue on Windows machines. I have also tried adding a delay of 1 second after adding the attachments. Still, I am facing this problem. The issue has also become very frequent.


The send or update operation could not be performed because the change key passed in the request does not match the current change key for the item., Cannot submit message.SaveStatus: IrresolvableConflict

Can someone please advise what can be done to avoid this error?