FullArc Verify

The process, in plain sight

A small conversation.
No email sent.

We open an ordinary email delivery conversation and end it before any message could be submitted.

The SMTP conversation

FullArc Verify connects to the receiving mail server on port 25 and asks about a recipient address. A typical exchange; real servers word their replies differently:

server  220 mx.example.com ESMTP
us      EHLO probe.getfullarc-verify.com
server  250 mx.example.com
us      MAIL FROM:<verify@getfullarc-verify.com>
server  250 OK
us      RCPT TO:<someone@example.com>
server  250 OK              <- there is a mailbox
us      QUIT

Where it stops matters.

We never send the DATA command, which is what starts a message. No message body is ever submitted or delivered.

We may also ask about one address that cannot exist. If the server accepts that too, it accepts every address (a “catch-all”), and its answer about a real address proves nothing either way.

What the answers mean

Valid

Accepted

The server accepted the mailbox, and does not accept everything.

Invalid

Rejected

The server said there is no such mailbox, or the domain cannot receive mail. The customer’s campaign does not email it, and it goes on that customer’s do-not-email list.

Risky

Unprovable

A catch-all server, or a provider that never says either way. Probably deliverable, but not proven.

Could not be checked

No answer

The server refused us, did not answer in time, or asked us to try later. A verified campaign does not email these addresses.

Our operating limits

  1. One list at a time. FullArc verifies one list at a time, across all of its customers.

  2. Controlled concurrency. At most eight mail domains at once, and up to 20 addresses in one connection. Microsoft-hosted mail gets one address per connection, which is what it accepts.

  3. Answers are reused. A definite answer is kept for 30 days, so the same address is not asked about again, whichever customer asks.

  4. Refusals are respected. After a refusal or a timeout we wait at least a day before asking about that address again. When a server asks us to try later, we wait at least 30 minutes, as asked.

  5. Opt-outs are absolute. An opted-out domain or mail host is answered for without connecting to it.

Where addresses come from

FullArc customers check their own contact lists before an email campaign. This service does not collect, buy, generate, guess or sell email addresses.

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