Here is our scenario: My company is responsible for mailing physical paper packets to CustomerCompanyemployees of. Some of these packages were incorrect. We now need to send an email to all of these employees with a PDF attachment correcting the problem, approximately 200 emails. CustomerCompany provided us with a list of email addresses. Users have not explicitly opted for any email from us and most employees probably don't know who My company East.
Are we at an increased risk of being reported as spam, as users don't expect emails from us? We may use a separate messaging service if this is the case, so as not to damage our reputation.
Is this a bad practice and / or illegal, given that the employees have explicitly opted for nothing? I understand that there are participation laws, but I think this does not apply, as these are not marketing emails.