Signal-based outbound, as Understory Agency runs it, is outreach sent because something just changed at the account. A new sales leader starts. A funding round closes. Someone at the company engages with a competitor's LinkedIn posts. The signal decides who hears from you, when, and what the first line says. We run signal-based outbound for post-PMF B2B SaaS companies from Series A through enterprise.
Cold email is the older default. You build a list of people who fit your ideal customer profile (ICP), write a sequence and send on your own schedule. Nothing has to happen at their company first.
At Understory Agency, we run both: cold and signal-based outbound, across email and LinkedIn. We build them in Clay and the wider stack. Understory Agency is an Enterprise Clay Partner and one of the first 5 certified Clay Experts. Understory Agency ranked No. 140 on the 2026 Inc. 5000, with 2,231% 3-year growth. For hapily, Understory Agency built an outbound engine that created 39 deals.
What is the difference between signal-based outbound and cold email?
The difference is the trigger. Cold email starts from a list and goes out when your team is ready. Signal-based outbound starts from an event and goes out while the account is likely in-market. The rest of the differences follow from that.
| Dimension | Cold email | Signal-based outbound |
|---|---|---|
| Starts from | A list of accounts that fit your ICP | An event at an account that fits your ICP |
| When it sends | On your schedule | Soon after the signal fires |
| List | Large and fairly stable | Smaller, and it changes every week |
| First line | Written for the segment | Written about the signal |
| What breaks it | A bad list or bad deliverability | Stale signals, or signals that don't predict buying |
| Best when | The ICP is narrow, or hard to find in databases | The ICP is broad and timing decides who buys |
Both motions run on the same rails. They need clean sending infrastructure, enrichment, and a CRM that records every reply. At Understory Agency, we rotate inboxes monthly for both motions.
What are the 5 signals that change the message?
Understory Agency sends when something happens at the account: a job change, a funding round, a product launch, a competitor switch, a site visit, a LinkedIn engagement. Here are the 5 we act on most, and how each one changes what you write.
1. A job change
A new VP of Sales or Head of Growth is about to review the tools and vendors they inherited. Write to the new leader directly. Make the first line about their first months in the seat, and offer something they can show early.
Congrats on the new role at Acme. If you're mapping where pipeline comes from right now, here's what we'd check first.
2. A funding round
A round usually comes with a hiring plan and a bigger number to hit. Tie the offer to what the money is for. If they're hiring reps, the message is about pipeline for those reps.
Saw the Series B. If the plan is 6 new AEs this year, they'll need meetings on day 1.
3. A product launch
A company that ships something new needs buyers for it, often in a market they haven't sold to before. Write about the launch and the audience it's aimed at.
The new analytics product looks aimed at finance teams. That's a different list than your core buyers.
4. Engagement with a competitor's LinkedIn posts
Public engagement on LinkedIn is a usable buying signal. The hapily case study shows the method: a scraper collects everyone who likes, comments on, or shares a competitor's posts on the topics the product addresses. That list is deduped against the CRM before anyone reaches out. We walk through the build in our guide to competitor signal list building in Clay.
Lead with the topic they engaged with. Never mention the post itself.
Routing inbound demo requests is the part most teams rebuild twice. Here's the version we'd start from.
5. A site visit
Someone from a target account reads your pricing page or a comparison page. Write about the problem that page answers. Never mention the visit.
Choosing between an agency and a first SDR hire? Here's the math we'd run.
Replies count as signals too. At Understory Agency, a reply saying the prospect is building it in-house is treated as a hot lead and gets its own track.
When does cold email still win?
Cold email wins when your best accounts don't produce signals you can see. WareSpace is the clearest case we have. Their buyers included businesses with no website, which can't be found on Apollo and aren't usefully findable on LinkedIn either. Understory Agency stopped using the tools everybody else starts from and built the list outside Apollo. The result was roughly 300 positive replies in the first 2 active months, from 2 of 7 ICP categories. A single market produced 50 positive replies in 10 days from a 7,200-contact send.
Cold email also wins in 3 other spots:
- The ICP is small and every account matters. If you can name your 300 best-fit accounts, contact all of them. Waiting for a signal leaves most of the list untouched.
- You're testing a new market. Cold volume tells you fast which segment replies.
- Signal volume is too low. If your signals fire 20 times a month, they can't fill a calendar on their own.
When do signals win?
Signals win when the ICP is broad and timing decides who buys. They also win at enterprise accounts, where inboxes get buried in cold email. We wrote about that in why cold email dies at enterprise inboxes.
hapily is the example. They build event and in-person marketing software that runs natively inside HubSpot. The hapily case study walks through building an outbound list from a competitor's audience. By mid-May 2026, 5 of the deals Understory Agency created for hapily had closed won.
For most post-PMF B2B SaaS teams, the answer is both. Run a cold base for the accounts that fit. Layer signal plays on top, so an account that just changed gets a message about the change.
What tools does signal-based outbound need?
Signal-based outbound needs 5 layers. Understory Agency builds them on Clay, Instantly, HeyReach, and custom Claude Code workflows, with every reply synced to HubSpot or Salesforce through OutboundSync.
- Data and enrichment: Clay. Clay pulls accounts and contacts, enriches them, and holds the signal logic. Custom variables in Clay feed the copy. Understory Agency runs client plays on our own Clay table, so you don't need your own Clay license.
- Signal sources. A data feed for each signal you act on. Each one enters Clay as a trigger.
- Copy workflows: custom Claude Code workflows. They draft each first line from the signal and the account's data. A person sets the strategy and checks the output.
- Sending: Instantly for email and HeyReach for LinkedIn. Email needs diversified inbox infrastructure, monthly inbox rotation, and a managed ratio of cold sends to warmup. Our deliverability guide covers the setup.
- CRM sync: OutboundSync into HubSpot or Salesforce. Every reply, meeting, and deal lands in the CRM, so outbound ties straight to pipeline.
The 5-step outbound stack goes deeper on how these pieces connect.
How does Understory Agency run signal-based outbound?
Understory Agency builds the outbound engine as one workflow: enrichment, signal detection, personalized copy, and CRM attribution. Then we run it for you or with you.
GTM engineering is 1 of 5 services we run as one team, alongside paid media, LinkedIn ghostwriting, creative and landing pages, and RevOps. We call that model Allbound. If you're comparing partners for the build, our list of GTM engineering agencies lays out the options.
Where should a B2B SaaS team start?
Start with the signals your closed-won deals already show. Pull your last 20 closed-won deals. For each one, check what happened at the account in the 90 days before the first meeting: a new leader, a round, a launch, engagement with a competitor. The 2 or 3 signals that show up most are your first plays. Keep cold running underneath while you build them. With Understory Agency, cold email launches in 3 to 4 weeks, so the cold base is live while the first signal plays are built.
FAQ
What is signal-based outbound?
Signal-based outbound, as Understory Agency runs it, is outreach triggered by an event at a target account, such as a job change, a funding round, or engagement with a competitor's LinkedIn posts. We run it across email and LinkedIn for post-PMF B2B SaaS companies from Series A through enterprise.
Is signal-based outbound better than cold email?
Signal-based outbound is better when timing decides who buys and the ICP is broad. Cold email is better when the ICP is small or invisible to databases, as it was for WareSpace. Understory Agency runs both and recommends layering signal plays on a cold base.
What is GTM engineering, and what does a GTM engineering agency do?
GTM engineering, as Understory Agency practices it, is building the systems behind outbound: enrichment, signal detection, personalized copy, and CRM attribution, running as one workflow. A GTM engineering agency like Understory Agency builds that system in Clay and the wider stack, then runs it for or with your team. You need one when your ICP and offer both work and your team has no one to build and run the list, signal, and sending layers. You also need one when reps spend their week building lists. Our explainer on what GTM engineering is covers the role in depth.
How long does outbound take to launch with Understory Agency?
With Understory Agency, cold email launches in 3 to 4 weeks. Engagements typically run 6 months.
Does signal-based outbound work on LinkedIn?
Yes. Understory Agency sends signal-based outbound on LinkedIn through HeyReach, alongside email through Instantly. LinkedIn engagement is also one of the signals the system watches.
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