Send Exchange Mail Message - mailing failure

Hi all.
Can anyone help me to know where this error comes from?
It only happens in production, I think it is with some specific email that they use in Production.
But I can’t replicate it in QA or Dev, and I can’t find profitable information.

Error Log:
d_arrow_down Raw message: Object
message: Send Exchange Mail Message: At least one recipient isn’t valid., Recipient ‘’ is not resolved. All recipients must be resolved before a message can be submitted.
level: Error
logType: Default
timeStamp: 2021-01-13T17:03:01.6591967-06:00
fingerprint: 5a24a893-babf-4a9b-abcb-711382156d07
windowsIdentity: bmvcorpcommx\ROBOTRPAINDEVAL
machineName: EC2AMAZ-MVF2DVK
processVersion: 1.3.2
jobId: 31f14570-ccc0-447e-80aa-dd79b9d84fba
robotName: Prod_Robot_Oper-001
machineId: 1
organizationUnitId: 1

This error is coming from the “Send Exchange Mail Message”. The issue is that Office 365 thinks that one or more recipient isn’t valid. Please check that the email recipients all exist. It is likely just a typo in someones email.

Hi, thanks, yes, we check all emails recipients exist and are valids… This is the reason for why i dont understand the error.

But i will be check again and others possible options…

This error can be for write a space between emails, example:

Correct: To:";"
Incorrect: To:";"

The activity “Send Outlook Mail Message” does allow spaces but “Send Exchange Email Message” don’t allow

Hi, welcome to the community.

Yes, i hace the mails in Asset like a correct format.
Correct: To:";"

The problems is random, i have 1 mount without problems… i continue checking what happent.