I have a problem / doubt about sending newsletters. I use Mautic in version 2.16.3 and I configured the smtp server using the Amazon service. The configuration is correct and has been tested.
Last week I sent a newsletter to 450 contacts and everything went smoothly, but today I sent one to all my contacts (25,000) and, despite the fact that all the emails have been sent, none of this is read.
Can you give me suggestions?