Founders build investor lists from directories, databases, LinkedIn and portfolio pages, then email them. The quiet assumption underneath is that the addresses work. To find out how often that assumption holds, we ran mailbox-level verification across the published email addresses of the investor contacts on the dealOS platform: 16,311 addresses checked, each tested against the receiving mail server rather than just for format.
The results are worse than most founders expect.
The numbers
| Verdict | What it means | Addresses | Share |
|---|---|---|---|
| Deliverable | Mailbox confirmed, email will arrive | 11,645 | 71.4% |
| Dead | Mailbox gone: hard bounce guaranteed | 2,761 | 16.9% |
| Catch-all | Domain accepts anything: unprovable either way | 1,445 | 8.9% |
| Unverifiable | Server refuses verification checks | 460 | 2.8% |
Put simply: one in six published investor email addresses no longer exists, and a further one in nine cannot be confirmed. Fewer than three quarters of the addresses a diligent founder collects will verifiably deliver.
Why the dead sixth matters more than it looks
A 17% bounce rate is not a 17% problem. Mailbox providers score sending domains on bounce behaviour, and hard bounces are the strongest negative signal there is. Send a wave of 200 outreach emails from an unverified list and roughly 34 of them bounce in the first hour. From that point, some of the valid 166 start landing in spam, because the sender now looks like a list-buyer.
The cruel part is how this reads from the founder's side. The investors who never received the teaser are indistinguishable from investors who ignored it. Founders conclude their deck is weak or the market is cold, when a sixth of their list was unreachable before they wrote a word. It also poisons the metrics that should guide the raise: open rates and view rates only mean something over the emails that arrived, a point we come back to in how to follow up with investors.
Where dead addresses come from
- People move. Venture and corporate development are high-churn careers. An associate's address from a two-year-old directory listing has decent odds of being retired.
- Firms rebrand and merge. Whole domains die, and every published address on them dies together.
- Databases decay silently. Contact databases are snapshots. Without re-verification they only get worse, and most sources never re-verify.
- Catch-alls mask the rot. Nearly 9% of addresses sit on domains that accept everything, so even a test send tells you nothing: the mail is accepted, then may be discarded unseen.
What founders should do with this
Verify before the first send, not after the first bounce wave. Mailbox-level verification is cheap compared with a burned sending domain, and it converts "why is nobody replying" into a real number: how many people actually received the teaser. This is why dealOS verifies investor emails before they become sendable at all; the platform's investor matching only surfaces investors whose addresses passed verification, and outreach is paced to protect deliverability from the first email.
Treat catch-alls as a separate tier. They are not dead, but they are not confirmed. Send to them after your verified tier, watch engagement, and prune the silent ones sooner.
Budget list size for decay. If a seed process needs 150 reachable investors, a raw list needs to start closer to 200. Our guide to building an investor list covers sizing and tiering in detail.
Date-stamp everything. An address verified nine months ago is a rumour, not a fact. Re-verify before each new raise.
Reuse this data
These figures may be cited freely with a link to this page as the source. The headline stat, for reuse: 17% of published investor email addresses failed mailbox verification in a 16,311-address check by dealOS (2026). We plan to re-run the analysis periodically and track how the decay rate moves.