Unknown results

An address is Unknown when the receiving mail server didn't give us a clear yes or no.

Why it happens

• The server was slow or timed out. Some servers take a long time to answer, or don't answer at all.
• Greylisting. Some servers deliberately turn away the first attempt from anyone new and only accept a retry later.
• Temporary blocks. A server may refuse checks for a while if it's busy or cautious.

None of this means the address is bad. It just means we couldn't confirm it either way.

What to do with them

• Small number of Unknowns: leave them out of this send, which is what the default clean list does.
• Important contacts: check a few of them individually with Check one email. Single checks are free when the answer isn't definite.
• Lots of Unknowns from one domain: that company's mail server is probably being cautious. Try those again in a day or two in a smaller file.

To include Unknowns anyway, switch on Couldn't confirm in Build your clean list.

Do Unknowns use credits?

Yes. Every unique address in an uploaded list uses one credit, whatever the result, because we've done the work of checking it.