Well, I would say the best success I have had with cold email outreach was a few years ago when I was still offering page speed optimization services for agencies. And all I did then was cold outreach for all the clients I converted
What made it work so well was the effort I put into each one of the outreach emails I sent out back then.
What I would do was audit an agency's site through GTmetrix. Thank goodness back then GTmetrix was totally free and you could run an unlimited number of audits, unlike now : D
So yeah, I would run an audit and send the outreach email with a screenshot attached, along with a couple of issues explained about what needed to be fixed.
All of this had to be done manually, auditing each site, taking screenshots and writing out the issues that needed fixing.
It was a lot of work and effort for just one email to be sent but it was so worth it for the conversions.
I mean, in terms of conversion, the ratio was still low compared to the number of emails I had to send. But the sweet spot with targeting agencies was that they already had clients they could just outsource to me.
So converting just one agency back then was a big, big win and I had so much success doing that.
I worked with a lot of big digital marketing agencies back then, with them outsourcing their clients' sites to me for optimization. I even worked on a couple of government websites for an agency : D
Oh, not to even talk about referrals from those agency owners or CEOs
I still have one client right now that I help with keeping their WP site running. The client has actually retired and since they stopped SEO and marketing with one of the agencies few years ago now, all they needed was to keep the site up and running while they ramped down their business for retirement.
The agency just passed the client over to me instead so I could manage their site for them
I stopped offering page speed optimization services a few years ago and pivoted into other things since... because after some time, there were more sophisticated ways of handling speed optimization all over the place.
It was fun, fun years back then : D
I still have that page speed optimization business site up to this day just because of the one client I still have there for WP management. It's a monthly subscription, so it covers the expense of still having the site up and all that.
I had more sweet success with other services and businesses I started after the speed optimization days too, using cold outreach both through email and social media, especially Twitter back before it became X.
But maybe we leave those stories for another day : D