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:
- Create a clear naming convention for your One Time Use lists, so that they can easily be recognized. For instance, all of the shuld be in the form of YYMMDD-OTU-List name
- Create a smart list using the "lead was created" filter and the "List" constraint. The filter would look like this:
it would give you the list of least that were really created when you imported the lists
- Use this smart list as an exclusion list for all you other programs and smart campaigns. This will require lots of discipline from your users
- Use this smart lists as a choice criteria if you decide to suspend them or black list them.
Notwithstanding the other suggestions, I have one which I've posted here to the same question several times.
- Upload as Static List
- Send your email
- Delete all Leads that are not MQL or above (or customers in case they are dupes).
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
- identify leads that should be removed in the near future to comply with your contracts.
- exclude from all other sends (without affecting a more serious emailable flag like Suspended)