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Ashvin Jadhav 13Ashvin Jadhav 13 

(Undelivered): 550 An internal error occured

Trying to send an email to service desk, but emails are getting bounced with error email stating the undeliverable. Following is the line from error email from Salesforce.  

Authentication-Results: apex.salesforce.com; dkim=fail (signature verification failed)

This issue occuring only when email or email replies had attachments, plan text emails are getting sent to cases. Also in email services Accpet Attachments setting has been kept to "All". 

Kindly help. 

Thanks & Regards,
Ashvin