There are email addresses in our database that we know are valid emails because our teams are communicating with them regularly, but emails to them from Marketo bounce regularly and repeatedly, causing them to be suspended by our bounce policy. How is everyone else dealing with these? Or is this a problem that most other people don't have? Also, for reference, we have a Marketo Dedicated IP so that (in theory) shouldn't be related to our issues.
Some of these happen within our ABM accounts - which are our most strategic accounts. What we've found is these companies are blocking ALL emails sent from Marketo - so having them whitelist emails sent from us isn't a solution. We then tried another approach (as suggested by Marketo's deliverability team) - by having the account whitelist a regex version of the Return Path header (e.g., "xxx-xxx-xxx.(\d+.)*\d+@em-sj-77.mktomail.com" - where "xxx-xxx-xxx" is our Munchkin account ID). We had one account that agreed to work with their IT department to implement - but that didn't even work. I wish there was a simple answer here - especially as we're finding more and more of our key accounts block our (Marketo) emails.