Outbound Reply Rates by Email Gateway: The Data

A sequence can be well written, well targeted, and still underperform for a reason that has nothing to do with the message: outbound reply rates by email gateway differ so sharply that two lists of identical quality can produce wildly different results depending on what sits in front of the prospect's inbox. Danish Lead Co. tracks the receiving mail gateway on every prospect record it processes, and the gap between a plain Google Workspace inbox and one sitting behind a secure email gateway is large enough to explain a lot of "this campaign just is not working" conversations.

This is for anyone running or auditing an outbound system who has watched reply rates vary by account with no obvious pattern in the message or the industry. The pattern is usually sitting one layer down, in the infrastructure the prospect's own company put in front of their inbox.

What Is a Prospect Email Gateway, and Why Does It Affect Reply Rates?

A prospect email gateway is the mail infrastructure a company runs in front of its inboxes, whether that is a mainstream provider like Google Workspace or Microsoft 365, or an added secure email gateway such as Proofpoint, Mimecast, or Barracuda layered on top for filtering. It matters because a gateway decides whether a cold message reaches the inbox at all, lands in a spam or quarantine folder the recipient never checks, or gets stripped of anything that looks like an unsolicited sales message before a human ever sees it.

Do Google Workspace Prospects Reply More Than Microsoft 365 Prospects?

Yes, by a wide margin: across 232,497 Google Workspace prospect records Danish Lead Co. processed in a recent 90-day window, 519 produced a qualified positive reply, a 0.22 percent positive rate, compared with 135 positive replies out of 311,900 Microsoft 365 records, a 0.04 percent positive rate. That is roughly five times the positive rate on Workspace, using comparable record volumes on both sides, and it holds before any secure gateway is added on top of either provider.

\* Combines Proofpoint, Mimecast, Barracuda, Cisco IronPort, Sophos, Trend Micro, Fortinet, Symantec MessageLabs, Forcepoint, and other named secure gateways, all layered on top of a base provider.

Do Secure Email Gateways Like Proofpoint or Mimecast Block Outbound Replies?

They do not block delivery outright in most cases, but they suppress replies dramatically: prospects sitting behind a combined secure email gateway replied at a 0.02 percent positive rate across 132,642 records, roughly a tenth of the Google Workspace rate and about half the Microsoft 365 rate in the same window. Proofpoint alone accounted for 62,254 of those records and only 10 positive replies, and Mimecast produced just 4 positive replies across 38,170 records. These tools are built to catch exactly the kind of message a cold outbound sequence sends, so a lower reply rate on those domains is the product working as designed, not a sign the message was wrong.

Why Does This Happen?

• Filtering, not just spam scoring. Secure gateways like Proofpoint and Mimecast run pattern and sender-reputation checks specifically tuned to catch unsolicited outreach, on top of whatever spam filtering the base provider already does.
• IT-managed environments correlate with company size. Larger companies are more likely to run a dedicated secure gateway, and larger companies already reply less to outbound for reasons unrelated to email infrastructure, which compounds the effect.
• Fewer humans see the message at all. A quarantined or heavily filtered message often never reaches a prospect's actual inbox view, so the lower reply rate reflects reduced visibility as much as reduced interest.
• Workspace and self-hosted domains skew smaller. Companies on plain Google Workspace or a self-managed mail server are frequently smaller organisations where a founder or owner is more likely to see and act on the message personally.

How Should This Change an Outbound System?

A system built without accounting for gateway differences will misread a filtering problem as a targeting or messaging problem, so the fix is in how the list and the expectations are built, not the email copy. Danish Lead Co. adjusts for this in three steps:

1. Set reply-rate expectations by account, not by campaign average. A blended reply rate across a list that mixes Workspace and heavily gated enterprise domains will understate how well the message is actually working on the accounts most likely to see it. Reading outbound reply rates by email gateway account by account, instead of as one blended campaign number, is what catches this before it looks like a messaging problem.
2. Treat secure-gateway accounts as a longer, multi-touch track. Where a target account is known to run Proofpoint, Mimecast, or a similar tool, plan for more sequence steps and other channels alongside email rather than judging the account on email replies alone.
3. Prioritise deliverability infrastructure everywhere it can still make a difference. Sender reputation, domain warm-up, and inbox setup matter most precisely on the Workspace and self-hosted domains where a message has the best chance of being seen, so that is where infrastructure investment pays off fastest.

Danish Lead Co. builds this gateway awareness into the outbound systems it runs for clients across manufacturing, B2B SaaS, and private equity and M&A accounts, where the mix of enterprise and mid-market targets means gateway type varies account by account within a single list. The same multi-touch, multi-country approach helped an aviation supplier open 53 qualified conversations across 30-plus countries in 46 days, a target list where mail infrastructure varied as much by country as by company size.

Conclusion

Outbound reply rates by email gateway are not noise in the data, they are one of the clearest structural patterns in it: Google Workspace prospects replied roughly five times more often than Microsoft 365 prospects, and secure-gateway prospects replied at about a tenth of the Workspace rate in the same window. A system that accounts for this treats a quiet enterprise account behind Proofpoint differently from a quiet small-business account on plain Workspace, instead of concluding the message failed on both.

Key Terms Glossary

Ready to Build a System That Accounts for Gateway Filtering?

If your reply rate looks inconsistent across accounts and you are not sure how much of that is the message versus the mail infrastructure sitting in front of it, book a call with Danish Lead Co. We will look at the gateway mix across your actual target accounts, show you which segments of your list are being filtered before a human ever sees the message, and you will leave with a system built around that reality, backed by the same reply data behind this post and the results behind Danish Lead Co.'s 5.0 rating across 32 reviews on Clutch, Trustpilot, and Google.

Related reading

• Google Bulk Sender Requirements: A Cold Email Checklist
• How to Improve Cold Outreach Reply Rates in 2026
• The Real Reason Your Outbound Reply Rates Are Low