Test your email: test newsletter spammyness with mail-tester
The test includes a reputation test of your ESP, coding quality of the email itself as well as a link-tester. An example result can be found here.
With ISPs (including webmail providers Gmail, Outlook.com and Yahoo) and other email handling platforms tightening their deliverability thumb screws, it’s important to check your email marketing messages for spammy content, proper email server authentication and any errors in your coding or links.
The way it works is to send an email to a designated address at mail-tester, after which a report will be created. The report will look like this:
This result shows the authentication part expanded: things like SPF and DKIM are described in detail.