We perform several checks and verifications to determine whether an email address is valid or invalid. We do a DNS verification and MX lookup, a SMTP check, and use our internal database along with proprietary algorithms to determine the validity of an email address. For more info, look here.
All emails in your validated list are given an Email Assurance Grade. 'Accepts-All' results are given a grade of B and 'Indeterminate' results are given a grade of D.
"Accepts-All" results are given an Email Assurance Grade of B - these email addresses are commonly seen in businesses and in many cases, the server will accept all mail and then bounce it back to sender, which in turn hurts the sender's IP Reputation.
Emails labeled as 'Indeterminate' cannot be confirmed as deliverable. These emails are ambiguous in nature because they may have more than one meaning.
In checking for an email, we were not able to do anything. The email address seems to have a mail server that is running and accepting connections, but we are unable to connect. We do not recommend sending to the "Indeterminate" category. All emails with a grade of D should be segmented off your list.
We do not recommend deploying email to this category right away. These emails are NOT included in the downloadable Safe List. But, if you linked an ESP account, we include these emails in your uploaded results because they may have more than one meaning, and therefore may be able to be verified in the future.
We recommend creating a segment within your list named "Accepts-All" and attempt sending this group a re-engagement campaign. If you can confirm that the addresses are "valid" and deliverable, try trickling them back into your list, so it does not affect your list's deliverability.
After uploading results to your ESP, we recommend that you segment the list by the Safe category (only A+ and A results), 'Accepts All' category (B results), and the 'Indeterminate' category (D results). Create segments for for each of these Email Assurance Grades to keep your emails separate and make sending to the "safe" category much easier. If you are a MailChimp user, you must segment!
Only Send to the Safe category.
After having a list cleaned with us, you should deploy campaigns ONLY to the Safe emails. If you are a MailChimp user, they do not recommend sending to 'Indeterminate' or 'Accepts- All' emails and may continue to send you warnings or block you from mailing if you deploy to these categories.
Send a Re-Engagement Campaign for 'Accepts-All' emails.
As mentioned above, 'Accepts-All' emails are ambiguous and can have more than one meaning. We do not recommend sending to them immediately, but you can send a re-engagement email to those with an Email Assurance Grade of B. If confirmed as valid and still engaged, you can trickle them back into your Safe segment slowly.
Do not send to 'Indeterminate' email addresses. Email addresses that have an Email Assurance Grade of B can be sent a reengagement email, but not those in the Indeterminate category with a grade of D.