Why catch-all domains keep burning cold email senders and how I finally fixed my bounce rate
catchall_fix_marco · 2026-07-30 · 1,020 views
I've been cold emailing for four years. For three of those years I included catch-all domains in every list I built. Bounce rate was a constant problem and I couldn't figure out why my ZeroBounce results weren't matching reality.
Catch-all domains are configured to accept email for any address, valid or not. When you verify a list, email verification tools can't determine whether a catch-all address is actually deliverable. They mark it as catch-all and move on. Most tools, including ZeroBounce, return a catch-all or accept-all result rather than valid or invalid.
The problem: when you send to those addresses, some are real and some are not. The ones that don't exist bounce. At high enough volume that bounce rate tanks your domain reputation fast. My bounce rate on campaigns that included catch-all domains averaged 4.8 percent. On campaigns with catch-all addresses excluded it averaged 0.7 percent.
My current workflow: ZeroBounce first pass to remove invalid addresses. Then I filter out all catch-all results entirely. I only send to verified addresses that come back clean. My lists shrink by roughly 20 to 35 percent depending on the industry, but the quality is dramatically better.
For industries with high catch-all rates, like financial services and legal, I run the list through MillionVerifier as a second pass. Their catch-all detection algorithm differs slightly from ZeroBounce and sometimes recovers 5 to 8 percent of addresses as sendable.
If you're including catch-all addresses in cold email campaigns and your bounce rate is above 2 percent, start there. It's almost certainly your catch-all rate driving the problem. Cut them and watch your domain reputation recover within two to three weeks. PuzzleInbox's spam checker will show you the difference in inbox placement once your bounce rate comes down.