Primarily, GlockApps tests the technical part of your email sending system.
If your message successfully passes through GlockApps checkpoints, then you can be sure that the technical aspect of your sending program is ok and your message has a chance to be delivered to the Inbox of your real recipients.
GlockApps analyzes the information received from the spam filters, message headers, content, and email placement and gives you the action steps that you can follow to improve your deliverability. You can take a look at the Action Steps tab in the report.
Mailbox providers will never tell you why they put the emails to the spam folder. When the GlockApps report doesn’t show any issues related to your sender authentication, spam score or message content, but the email placement shows the Spam folder for many or some mailbox providers, then it might mean that the reputation of your sending domain and/or IP address is not good with those mailbox providers.
The email placement depends on different factors: sender reputation, user engagement, message content, sending email address, domain, IP address.
Often times, it is possible to find out why the mailbox provider filtered the email to ‘Spam’ only after doing multiple email deliverability tests changing different things such as email templates, formats (text vs. HTML, with/without links and images), From names, email addresses, domains, and even email service providers.
Check out the guide on how to find out what is causing the ‘Spam’ email placement.