A contact list is OK to email using HubSpot if all of the following statements are true:
1. You have permission to email these contacts
Importing purchased or third-party lists where contacts have not explicitly opted into hearing from you can lead to poor email deliverability. Purchased lists are typically filled with people who don’t know who you are yet. When your email hits their inbox, they’re much more likely to mark your email as spam.
2. You have an unsubscribe or suppression list to go along with it
Email lists should always come in twos. When you import a new contact list into HubSpot, you should include an opt-out list from the same source. If you don't keep track of your your list may include unengaged contacts, which has a negative impact on your deliverability.
3. You have emailed these contacts within the past year
Email addresses that are over a year old bounce at a significantly higher rate than more recently acquired email addresses. Email addresses change as people change companies, ISPs, and last names. Emails sent to stale addresses are much more likely to be hard bounced or marked as spam.