When linked lists are purchased, they are uploaded directly to MailChimp, and contain all emails from your Email Assurance Report (with grades of A+, A, B, and D). Emails given a grade of F are undeliverable, so they are unsubscribed from your MailChimp list. Our recommendation is that you log in to your MailChimp account and create segments for'Accepts-All' emails, and 'Indeterminate' emails as a Safe Segment is created automatically.
We do not recommend sending to the 'Accepts-All' segment right away - but you can attempt a re-engagement campaign to emails with an Email Assurance Grade of B, and if any addresses in your 'Accepts-All' category are determined to be valid, you can then trickle them back into your Safe list very slowly!
We do not recommend sending to the 'Indeterminate' segment ever. You should create a segment for all emails with an Email Assurance Grade of D - but you should not deploy to them .
This list is not Safe to send emails to! Create a segment for the emails within your list that have an Email Assurance Grade of B - Deploy a re-engagement campaign to these emails ONLY and if they are determined to be valid and deliverable addresses, you can then trickle them back into your list slowly.
This list is never safe to send to! Create a segment for for emails within your list that have an Email Assurance grade of D - Do not deploy email to this segment!
Send a test email to this segment ONLY to test the deliverability of maybe emails.
From MailChimp: How can I save and use segments in my list?