I am trying to think of the best way to organize some lists we have coming thru. These lists are for a one time email only and should not be included into the general database unless they become MEL. I can add them into their own program and reference the program for any emails to remove those members, but I am wondering what are some best ways to do this seamlessly in Marketo that I would not need to continually cross reference to ensure the contacts are not on any mailing lists. Specifically ensuring any MCL's do not sync to SFDC until they are further in the funnel.
Not sure of the best way, but one way to accomplish this is by importing these leads into static lists and check them "marketing suspended". Before the email send, you can uncheck "marketing suspended" and send the email. And then immediately afterwards, check "marketing suspended" again to ensure they do not receive any other marketing emails. Make a note that operational emails can still be sent to marketing suspended leads.
If you want something stronger than supension, you can also blacklist them. If blacklisted, the operational emails won't be sent.
Another way would be to add them to a distinct partition if you have the feature.
With regards to ensuring that there are not inserted into SFDC, this is very tricky, because sync can happen event implicitly, for instance if you add them to a program as member and this program is sync'ed with a SFDC campaign.
The other issue is that, when you import a list, some of them might not be new leads and have already been in your Marketo DB for a while. And you do not want to suspend or blacklist these preexisting emails.
So, what I would do is:
Notwithstanding the other suggestions, I have one which I've posted here to the same question several times.
Now, it is entirely possible to also create a special flag, say "One Time List Send=T" and upload the new leads like that. You can then use this flag to