Think about who runs these domains. Accept-all mail is common at mid-sized companies, at firms behind a hosted mail gateway, and anywhere an admin decided that catching misdirected mail beat rejecting it. None of that says whether your contact works there. Our catch-all glossary entry explains the setting.
The risk is real but bounded. Some catch-all addresses are wrong, so mailing them lifts your bounce rate above what a fully proven list would give. How much depends on where the addresses came from, and you can measure it on your own sends.
Send in two groups. Mail your valid addresses as the main campaign, send the catch-all group on its own, and compare the two bounce rates. Keep hard bounces under 2% overall. Two rounds of this tell you what that data source is worth, which beats any vendor's guess.
Source is the strongest signal you have. An address a person typed into your form is mostly right, even on a catch-all domain. An address a pattern tool guessed as firstname.lastname@ is a different matter, and on a catch-all domain no check can tell which one is real. That's why no one can verify a catch-all email at mailbox level.
There's one case for holding them back. If your sending reputation is already damaged, mail only addresses you can prove for a few months. Once your numbers recover, bring the catch-all group back in small slices.
Two test sends, read side by side
Say your cleaned list has 14,000 valid addresses and 5,000 on catch-all domains. You mail them as two sends. The valid group returns 70 hard bounces, which is 0.5%. From the catch-all group you get 190, or 3.8%.
Blend the two and you get 260 bounces on 19,000 messages, a rate of 1.4%. That's under the 2% line, so keeping this catch-all group costs you little. Now change one number. If the catch-all group had bounced at 12%, that's 600 bounces, and the blend climbs to 3.5%. Same list size, very different decision.
Go one step further and split the catch-all group by where the addresses came from. You'll often find that form signups bounce at around 1%, while a bought or guessed segment inside the same group bounces somewhere in the teens. Keep the first and drop the second.
What deleting them costs, and a slower way to test
Put a number on the other side of the scale before you delete. Say each campaign turns 0.4% of recipients into a sales conversation. On 5,000 catch-all contacts that's 20 conversations per campaign, gone for good. A few extra bounces are usually cheaper than that, as long as you stay under the line.
If your sender reputation is healthy but you're nervous, don't mail the whole group at once. Send to 500 a day for ten days and check the hard-bounce count each morning. A bad source shows itself in the first slice, and you can stop with 4,500 addresses unmailed and no harm done.
Once an address in the group has bounced, suppress it for good. When one has opened or replied, move it into your main segment. After two or three campaigns the catch-all pile shrinks by itself, because most of it has sorted into proven good or proven dead.
Related questions
Should I send to catch-all emails?
Yes, as a separate batch from your valid addresses. Watch that batch's hard-bounce rate, keep the source if it stays under 2%, and suppress every address that bounces.
What bounce rate do catch-all addresses produce?
The rate depends on where the addresses came from. Addresses people typed into your form bounce little, while pattern-guessed ones bounce far more. Measure your own source with a test slice of about 500 addresses.
Do any verifiers resolve catch-all addresses?
Some estimate a likely answer from patterns and public data. That's a probability, and it deserves its own label so you can judge it, not a valid verdict.
When should I remove catch-all addresses?
Hold them back while you rebuild a damaged sending reputation, when every send needs to be provable. Bring them back in small slices once your bounce and complaint rates recover.