A cold email without a reason reads the same to everyone: "we do X, let's talk". An email with a reason reads differently: "you just opened a warehouse in Leeds, we have helped launch sites like that". A sales signal is an event inside a company that makes your product relevant right now.
Here are eight signals that work most often in B2B.
1. Hiring in the right team
A company is hiring three sales reps: soon they will need a CRM, training and leads. It is hiring data engineers: analytics is coming. Job postings show where the company is investing in the coming months.

What to say: name the opening and the problem of that new team you take off their plate.
2. A tender or purchase
An announced purchase is a direct request to the market. Even if you are too late for this one, the need and the budget exist, and the next purchase can be yours.
What to say: show you understood the requirements and offer to go through them before the next round.
3. New leadership
A new department head reviews vendors and processes in the first months. That is the best window to get on the list.
What to say: congratulate them on the role and offer a short review of what you see in their industry.
4. A new office, warehouse or plant
Expansion means purchases: from equipment and logistics to software and hiring.
What to say: tie your offer to the launch of that specific site and its timeline.
5. A product launch
A new product needs marketing, sales, support and integrations.
What to say: offer help with what comes after the launch, not help in general.
6. Funding or an acquisition
After a round or an acquisition there is money and a growth plan, and new purchases come with them.
What to say: build on the goals the company announced, not on the size of the round.
7. Entering a new region
New markets mean local partners, lawyers, logistics and sales from scratch.
What to say: talk about your experience in that particular region.
8. New regulatory requirements
A change in the law forces companies to change processes by a set date. The deadline works for you: the solution is needed by a specific date, not someday.
What to say: name the requirement and the date it has to be met by.
Why signals get missed
Every one of these signals is public, but scattered: job postings on some sites, tenders on others, appointments in the news. Tracking them by hand across a hundred target companies is close to impossible. Signal checks your target companies on a schedule and reports an event while it is still fresh, together with the people worth writing to.
