One of my clients was to send an email to ~100,000 recipients. The client is a state organization, the emails are not promotional, the recipients are all members of the organization and they are sure that the messages will not be considered spam by any human recipient. Additionally, this is a one-off event. They will probably need to send such an email again in a couple of years.
The problem is that the list is old and I'm estimating that around 10-20% (maybe even more) of the addresses will bounce back. As far as I know, such a large number of bounces will raise a red flag for services such as mailchimp, Amazon SES, etc. Am I correct in this?
By using their own mail server and following the practices outlined in various questions of this site (such as Sending 10,000 emails?, How to send emails and avoid them being classified as spam?, Best Practices for preventing you from looking like a spammer), will their server be blacklisted after the first few thousands of bounces?
If in both cases the high bounce rate will be a problem, is there any other way of doing this, sort of manually curating the list (which would mean making ~100,000 phone calls)?