Why is one search head able to send out email alerts but not the other?

[Golgie]

Hello Splunk Community, 

I have two search heads. 

1 search head is able to send out email alerts and the other one can't.

I am using Amazon SES as the Mail Host. Each Search Head has a unique Access Key and setup the secret key. 

I can't figure out why 1 of the search heads can not send an email out and the other can.  

I used the sendemail command on the server with the issue and this is the error message I am getting:

command="sendemail", (535, b'Authentication Credentials Invalid') while sending mail to:<myEmailAdress>

Thoughts? 

[yuanliu]

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I used the sendemail command on the server with the issue and this is the error message I am getting:

command="sendemail", (535, b'Authentication Credentials Invalid') while sending mail to:<myEmailAdress>

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You answered your own question: on that problematic server, credential is not set up correctly. (Did you get similar errors in splunk.log?)