For SMBs, you're looking at three main players: Smartlead, Instantly, and Lemlist. I've run all three at different scales.
Smartlead is the current community favorite for good reason. Their unlimited sending accounts model is perfect for SMBs who need volume but can't afford enterprise pricing. You can spin up multiple sender domains cheaply and their deliverability is solid if you warm properly. Pricing starts around $39/month for decent volume.
Instantly is the main competitor with similar features but slightly higher pricing. Their UI is cleaner and support is more responsive, but Smartlead edges them out on pure cost-effectiveness for most SMBs.
Lemlist sits in the middle ground - more expensive than the first two but with better native personalization features. If you're doing heavy image/video personalization, it's worth the premium.
All three integrate well with Clay for enrichment waterfalls, which is crucial for SMB operations where you need to maximize data quality without manual work.
The real differentiator isn't the tool - it's your infrastructure. Whichever you pick, invest time in proper domain warming, SPF/DKIM setup, and good suppression list management. Most SMBs fail because they rush the technical setup, not because they picked the wrong sending platform.
Start with Smartlead if budget is tight, Lemlist if personalization is critical. Both will scale with you through the first few million in ARR.