Catch-All Domain Detector
Catch-all domains accept any address; bounce verification looks clean but mail goes to a black hole. This tool flags the pattern.
# Get the MX
dig MX example.com +short
# Connect to the lowest-priority MX
telnet $(dig MX example.com +short | sort -n | head -1 | awk '{print $2}') 25
# In the SMTP dialog:
HELO yourdomain.com
MAIL FROM: <test@yourdomain.com>
RCPT TO: <xyzabc123nonexistent@example.com>
# If the server returns 250 OK → catch-all
# If the server returns 550/551 unknown → not catch-allCatch-all domains accept any address, so list-verification tools report "valid" for addresses that don't actually exist. Mail to a non-existent address on a catch-all domain goes to /dev/null without bouncing — your reply rate looks zero with no diagnostic signal.
Tests an obviously-fake address at the domain (e.g. xyzabc123nonexistent@). If the SMTP server accepts it, the domain is catch-all and your bounce-verification tool is lying to you.
Before trusting any bounce-verification result. Especially before sending to executive lists where catch-all is common.
FAQ
Why do companies run catch-all?+
To avoid losing mail addressed to typoed addresses, or to capture mail to former employees. Common at small companies; rare at large enterprises.
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Articles, glossary entries, and other tools on the same topic.
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We update these pages when the underlying mechanics change — new mailbox-provider rules, new tracker behavior, new measurement gaps. The dates above are real revisions, not auto-touches.