After upgrading emailgtw probe to v2.91 / 2.90 smtp email sending does not work. Getting authentication failure:
emailgtw: [HEADER] 535 5.7.3 Authentication unsuccessful
The same configuration works fine with the old version emailgtw 2.84
The "535 5.7.3 Authentication unsuccessful" indicates that the SMTP server is unable to verify the sender's credentials (username and password). This error can be caused by a compatibility issue between the emailgtw 2.90 and later versions and the Exchange Server 2010. Since the new versions of the probe only supports Exchange Server 2016 and 2019, it's using modern authentication protocols and features that are incompatible with Exchange 2010.
emailgtw (Email Gateway) Release Notes (broadcom.com) >> SEE: probe Specific Software Requirements
Since the version 2.91 supports only Exchange Server 2016 and 2019 either use emailgtw v2.84 if using MS Exchange 2010 or upgrade the Exchange server to 2016 or 2019 to use the functionalities of emailgtw 2.91 and later versions.