Declining Email Delivery %

What do you do with those hard bounces now?

You don't necessarily have to remove them from Marketo, especially if you end up putting them back in later, but you can mark them bounced and then remove them from receiving emails. This will help your delivered rate and your sender reputation. There's really no point in emailing if they are not getting the email anyway.

You can also look at the reason why the email is bounced. A bounce because the email address doesn't exist says you should either update the email address (maybe they were acquired or changed domains) or that the contact is no longer with the company. If the reason is because you were rejected as SPAM then that says that your declining delivery is part of a bigger problem...

some thoughts on this

Email Reputation Management Automation - Marketing Rockstar Guides

there are some posts on developing that further in my Guide.

One thing to do is sort out why they hard bounced. When you run a smart list, you can add the constraint "Category". Category 1 means you were rejected by the server as spam. Category 2 means the inbox doesn't exist (and they'll be marked by Marketo as Email Invalid = True). Then you can troubleshoot further. More Category 2s means you need to look at your sources of leads and if you're pulling in dirty data. Or maybe your database is aging. Category 1 means you have a reputation problem (and someone wiser than me can give you advice on how to handle that!).