This "how to" guide explains how to set up a vacation rule in Gmail.
Why am I seeing a Proofpoint URL when someone sends me an email that contains a link?
When someone sends you an email, it is scanned by Proofpoint for viruses, malware, and malicious links before it is delivered to your inbox. Links in emails you receive from outside SCU are rewritten with a Proofpoint URL that starts with https://urldefense.proofpoint.
If you click on a link to a malicious webpage, you will see a notice will appear letting you know the malicious website has been blocked.