About our mail server checks

If you found this server in your mail logs, it is Emailfortify’s address checker. It asks mail servers whether a mailbox exists so our users can remove dead addresses from their lists. It never sends email.

What it does

For each check it opens one SMTP connection to the domain’s mail server and has this conversation:

EHLO probe.emailfortify.com
STARTTLS                         (when offered)
MAIL FROM:<[email protected]>
RCPT TO:<address-being-checked>
QUIT

It disconnects after the RCPT reply. It never sends DATA, so no message is ever delivered to anyone.

To tell whether a domain accepts every address (a “catch-all”), it may also ask about one made-up address that starts with eft- followed by random characters.

How we keep it light

• At most two connections at a time to any one mail server, however large the list being checked.
• Results are cached for up to 30 days, so the same address isn’t checked again and again.
• Users must agree to our acceptable use policy, which bans checking bought, scraped or harvested lists.

Identity

• IP address: 18.144.159.25
• Reverse DNS: probe.emailfortify.com, which resolves back to the same IP
• HELO name: probe.emailfortify.com
• Envelope sender: [email protected]

Questions or problems

If these checks are causing trouble for your server, or you want them to stop for your domain, contact us with your domain and a log excerpt and we’ll act on it.