Why Cold Outreach?
In short, we do cold outreach because it's effective, it can produce results quickly, and, most importantly, it's extremely cost effective.
Before you get started, you should think about warming up a new email address so you don't run the risk of getting your main business domain/emails flagged as spam.
The easiest way to do this by following these steps:
1) Purchase a fresh domain. If your agency's domain is youragency.com, you could purchase something like youragency.co or your agency.mail, etc.
2) Create a GSuite account (visit gsuite.com and click "Get Started"), register the new domain in GSuite, then create an email for that domain in GSuite (something like firstname.lastname@example.org). Note, GSuite charges $6/month per email address.
3) Sign up for 10-20 newsletters/services using the new email address so that emails start naturally flowing into the account. Here are some good ones: Twitter, Moz, Unbounce, Convince & Convert, The Daily Carnage, Neil Patel, Seth Goden, Buffer, Marketing Drive, Total Annarchy, Sketchalaytics.
4) Send 10-20 emails to friends/family and make sure they reply.
After a few days of emails going in and out of your new email account, the email address and domain will be "warmed up" and ready to go.
You can learn more about warming up domains and IP addresses in this guide from Mailgun.