Non-marketable leads vs Database size, Data Limits and Black List

[Anonymous]

We are using marketo for quite a long time and it collect a huge base of ubsubscribers/bounced leads. Now it's cover our data limits on nearly 30%. But keeping in mind that this is non-marketable leads that didn't bring any profit - it's really sad to keep it in Marketo. 

I read a several topics here about that:
Discussion: https://community.marketo.com/MarketoDiscussionDetail?id=90650000000PUqMAAW
Idea: Master exclude list https://community.marketo.com/MarketoIdeaDetail?id=08750000000IXRVAA4 
Help article: https://community.marketo.com/MarketoArticle?id=kA050000000KzQh&src=comm 

But still have questions:

• Is it safe to think that if I will delete the lead Marketo will remember it's state? 
• Why those "dead" leads affecting data limit at all?
• Can we create a exclude email list instead of keeping those leads in marketo?

If we will be managing Exclude list outside marketo - how to deal with a follow-up system in marketo for those leads who will return through website forms?

Does anyone faceded same questions or have any idea how to deal with the questions above? 

Thanks.

[Josh_Hill13]

Possible solutions

1. Deleting a lead in Marketo deletes the lead. It is gone. Marketo forgets it.
2. Marketo only ignores unsubscribed=true and Anonymous. I recall someone saying they were no longer counting Invalids or something, but I doubt that because you can still use the record in other ways.
3. What do you mean by "master email"?
4. before you delete anyone, download their data to a separate area just in case.
5. Remember to Delete in SFDC as well because they will return to Marketo if you don't.
6. Create a hierarchy of bad data and work your way down.

• Dedupe first
• Trash/Junk
• Hard Bounced and No Activity
• Invalid Emails and No Activity
• No Activity in Past X Months
• Untouched by a sales person in X months

[Anonymous]

Thank you for your comment.

1. What do you mean by "master email"?

Sorry it's just my mistake, I mean "exclude email list": 

• Can we create a exclude email list instead of keeping those leads in marketo