This server checks whether email addresses exist. It never sends mail.

If you found probe.joomguard.com in your mail logs, it connected to your server, asked whether one specific address exists, and disconnected. No message was transmitted, because none was ever composed.

The technical details a log reader usually wants are directly below. Contact and opt-out are at the end of the page.

What the connection actually consists of

A verification probe is a deliberately incomplete SMTP conversation. It stops at the point where a normal client would begin transmitting.

What it does

Opens a connection to your MX on port 25
Sends EHLO, then MAIL FROM
Sends one RCPT TO for the address being checked
Sends a second RCPT TO for a random address, to detect a catch-all
Reads your reply code and disconnects

What it never does

Send DATA — no message body is ever transmitted
Deliver, relay or forward mail of any kind
Attempt authentication, or try to relay through you
Harvest addresses — it only checks addresses already published or supplied
Retry in volume: connections to one server are paced, and a server that declines is not contacted again that day

Why an address at your domain was checked

The addresses come from a business contact list — published contact addresses on company websites. Before anyone is contacted, each address is checked so that mail is not sent to one that no longer exists. Undeliverable mail harms the recipient's server and the sender's reputation equally, which is the reason this check happens at all.

A rejection from your server is a useful answer, not a problem. It is recorded, and the address is not used.

To stop this server contacting yours

Send either the domain you receive mail for, or the hostname of the mail server that answers for it. Subdomains are covered automatically, and a server name covers every domain behind it. No explanation is needed and none will be asked for.

The exclusion is entered on this server and takes effect on the next connection attempt — there is no queue and nothing to wait out. It does not expire, and it is never lifted automatically.

Blocking this IP at your firewall also works and needs nothing from us — the result is simply recorded as unreachable.

Contact

abuse@joomguard.com

Abuse reports, exclusion requests, and questions about a specific log entry. Include the timestamp and your domain and the exact connection can be looked up.

Operated by Saikot Hawlader — full-stack developer and Joomla security specialist, working with European clients since 2010, trading as JoomGuard.

JoomGuard · Saikot Hawlader · Nashrin Palace, Holding 2656, Road 9, House 11/5, Rupatoli Housing Estate, Barishal 8207, Bangladesh · +880 1717 996078 · info@joomguard.com

Provider identification (Impressum): joomguard.com/legal-notice · Privacy: joomguard.com/privacy-policy