I would begin by setting up Mail server settings in vCenter server.
Select your VC, go to Manage->settings->General
Double check if Mail settings are set, if Not, click on Edit and specify your email server with sender account name.
Now go ahead and modify an existing alarm or create a new alarm as per your need.
you got to just configure alarm action for 'Send me a Notification' email. Like I am editing following alarm
Since the incident could be related to different situation that would be handled by Vmware in terms of alarms
Currently, there's no SMTP authentication enabled through vCenter to send alarms straight through a service provider like smtp.google.com:
You may want to opt to run a local SMTP relay service/VM, which would send out messages to the Gmail account of your preference.
For vCenter v6.0, if you would like to enable SMTP authentication settings you could do so actually in the vCenter Server Settings -> Advance Settings :
KEY : VALUE
mail.sender : The alert email address e.g. firstname.lastname@example.org
mail.smtp.username : The valid SMTP account name e.g. email@example.com
mail.smtp.password : The valid SMTP account password
mail.smtp.port : The SMTP receiving port e.g. 25
mail.smtp.server : The SMTP host e.g. mail.mydomain.com
Hope this help. Not too sure if this is valid for v5.5 but for sure this is working for my current v6.0 environment that use plain SMTP authentication.