I'm going to argue against my own category for a minute, because if you're searching this you've probably already had an agency and you're probably searching because it didn't work.
You sign with an agency. You meet the senior person in the pitch, sharp, experienced, clearly good. You sign and you never speak to them again.
The work goes to an account manager who's carrying eleven other brands and the execution goes to a junior who's never seen your product. Six weeks in, the emails don't sound like you. Three months in, you're reviewing subject lines yourself because it's faster than explaining the brand for the fourth time. You've become the bottleneck in the thing you paid to remove the bottleneck from.
You're paying agency rates for junior output and doing the strategic thinking yourself. That's the model. It isn't a bad agency, it's just what happens when a business needs to make margin on people's time.
I'd rather be straight with you, because sometimes the answer is yes:
If that's you, hire an agency. Andzen and Email Experts are genuinely good at what they do and I'd point you at them without hesitation.
That's what I do. Sixteen years, Klaviyo and Omnisend, the flows and the campaigns and the strategy, built and run by the person you're actually talking to. No account manager, no handoff, no junior. One senior operator who owns the channel and answers for the number.
I take a small number of clients, which is the constraint that makes it work. It's also why I'll tell you if it's not a fit.
Send me your store and your platform and I'll audit the account for free. You'll get a specific read on what's broken and what to fix first and if what you actually need is an agency, I'll tell you that too.