Authentication Required
Prior to being able to send mail I continue to get an error message.The message states that the SMTP server response fails, and requires authentication. I am using a Mac book pro OS version 10.13.3 and have had this issue since the most recent update. Any help resolving this issue would be greatly appreciated.
Thanks!
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<Image Edited by Host to Remove Personal Information>
MacBook Pro with Retina display, OS X Yosemite (10.10.5)