Before we had Marketo we had a procedure of deleting the email addresses out of Saleforce so that they weren't pulled into email blasts. We noticed that if we delete and email in Saleforce now, it won't transfer any more information to the Marketo lead and it continues to email them. Has anyone else had this problem and if so, how do deal with it? What happens if an email is no longer good, but we don't want to delete the account?
Marketo basically requires the email field in order to create/maintain a lead record - since, at heart, Marketo is still an email marketing/nurturing system. When you have an invalid email, I highly recommend you mark it as "email invalid" in Marketo, and it will no longer get your email blasts. You can then use other campaigns to check if the email address is updated, and then mark the lead as no longer 'email invalid' if the email field changes.