A blacklist lists an IP or a domain because of mail it sent. A verification probe sends no mail. ZapBounce opens a connection on port 25, says EHLO, gives a MAIL FROM, asks RCPT TO about the address and reads the reply: 250 for accepted, 550 for no such user. It quits before the DATA step, so no message is written and no inbox receives anything.
Your own domain never appears in that conversation. The probe comes from the verifier's servers, not from the IP or domain you send campaigns from. Gmail and Microsoft judge you on the mail you actually send, and a check isn't mail.
Trouble starts when you run the probes yourself. A script that fires thousands of RCPT TO commands from your sending server looks like address harvesting to the receiving side. Gmail and Microsoft 365 block SMTP probes from cloud IPs, and most home ISPs block port 25 outright. So the script returns mostly errors while your IP picks up a bad record.
Skipping the check is the bigger risk. Mail to dead addresses comes back as hard bounces, and a rising bounce rate is exactly what mailbox providers and blocklist operators watch. Verifying first takes the invalid addresses out before your first send, which is why a cleaned list is the safer list to mail.
Run your list through bulk verification, send only the valid rows to your main campaign, and test your sending IP with the free blacklist checker. If you're already listed, why your domain is blacklisted covers what to do next.
Related questions
Does email verification send an email to the address?
No. The check stops at RCPT TO and closes before DATA, the step where a message body would be sent. The person on your list receives nothing.
Can verifying emails hurt my sender reputation?
Not when a verification service runs the check, because the probe comes from its servers, not yours. Your reputation is built on the mail you send, and a verified list sends fewer hard bounces.
Is it safe to verify emails from my own server?
It's risky. Thousands of RCPT TO probes from one sending IP look like address harvesting, and Gmail and Microsoft 365 block SMTP probes from cloud IPs. Most home ISPs block port 25 as well.