There are four states of validation for an email address in Email Address Checker.
Pending
The email address is being checked by our server. “Pending” time varies based on factors such as:
- How many emails are ahead of you in the server queue.
- If the email being checked resides on a server using “grey listing” spam protection, checking takes a little longer as we need to do multiple retries against the target mail server.
Ok
Means that the remote mail server (responsible for hosting the email address being queried), is saying that the email address is valid.
Note: On rare occasions, it is possible for a remote mail server to provide a positive response to checking an email address even if the email address does not exist. Some installations of Microsoft Exchange are known to do this. In our research, we have found the number of mail servers configured with this behavior is relatively low (somewhere in the region of 5 to 10% of a typical list of email addresses).
Bad
Means that either:
- The remote server returned a definite “mail does now exist” message OR
- The remote server is not available or timed-out during query
Unknown
Means that, for reasons outside of our control, our service has been unable to determine if an email address is valid. Possible reasons for this are:
- The mail server is known to have a non-standard configuration (e.g. Yahoo servers implement non-standard SMTP protocol sequencing)
- The mail server returned an unexpected response
We show “Unknown” status to show you that it’s not possible to determine if an email address is valid using our service.
Note: Mail server that are “Unknown” are a problem for all email address checking software & services whether the vendor chooses to make you aware or not. We choose to be upfront and say when it’s not possible to check an email address.
We have found that the number of servers responding “Unknown” is between 6 – 9% based on a typical list of emails. This figure can be higher/lower depending on whether you list, for example, contains lots of Yahoo addresses.
