Email Address is not a primary key, nor a uniquely indexed column, in the Marketo database.
It is frequently misstated as such, despite it being very easy to demonstrate that 2 leads can have, and/or be changed to have, the same Email Address value!
Email Address is a frequently encountered -- but not universal across the platform -- deduplication key for most methods of importing leads into Marketo. So when you use those methods, such as a form fillout or a UI-based CSV import, Marketo will merge into the database by pre-checking for a lead with the same Email Address.
But when you use other import methods, such as merely touching up a lead's Email Address in the Marketo UI, or using the API to import and telling it to dedupe on the Lead ID, Marketo does not care if the Email Address you enter is used by any number of other leads in the database.
Email Address is also used to restrict the number of unique leads who qualify for a Send Email activity, so you will not be flagged for spamming the same mailbox over and over with the same send. This restriction can be annoying in certain cases but is usually a good thing.
I thought that E-mail Address was primary key.
In addition, it may be synchronized with Marketo and SFDC.
The following data is registered in Marketo list. (There were data with different hospital names even though they are actually the same mail address)
Import the following leads into that list.
At this time, is there a standard on which lead data will change the company name (hospital name)?
* The rewriting of the Id is blocked by the system administrator.