Every address you check gets one of four labels. They are color-coded so you can scan your list at a glance.
Safe to send (green)
The address passed our checks and the receiving server accepted it without raising a warning. These are the strongest addresses in your results.
Risky (yellow)
Something about this address is uncertain. It might be fine, but it carries a warning sign — for example, the domain accepts every address it is offered, so we cannot be sure this exact mailbox exists. Send carefully, or hold these back from important sends.
Do not send (red)
We found a clear reason not to send — for example, broken formatting, a throwaway service, a domain that cannot receive mail, or a server that rejected the address. Remove these from your list.
Unknown (grey)
We could not get a clear answer this time — usually because the receiving server was slow or temporarily unavailable. This is not a bad address, just an unfinished one. Try checking it again later.
Tip
A simple rule of thumb: send to green, remove red, and decide case by case on yellow. See "What to do with risky addresses" for help with the yellow ones.
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If you still have a question, we are happy to help.