Unable to configure SMTP server as ssmtp was missed to be installed. 

(mistakenly reverted changes in update/avxsystem.ks file which installed ssmtp) 
Added the change to install ssmtp and also added a change to clear log alerts also when "clear log config"  is executed as this was the APV behaviour.

Tested in a different AVX which didn't have ssmtp installed previously

DV.a4niZEC(config)#system mail external server "smtp.gmail.com" 587 1
DV.a4niZEC(config)#system mail external user "arraynandita@gmail.com" "app_pass"

Mail received: 

arraynandita@gmail.com

​

Nandita Gurunathan​

Caution: This is an external email and may be malicious. Please be careful when clicking links or opening attachments.

CLI: User "array" executed cmd "sh log alert"