Mailster allows you to quickly test your campaigns with our precheck feature.

Consent Required
To use the Precheck service Mailster needs to send your campaign to our server. The email which is sent is the same as seen in the preview pane. All personalized information including links, images, attachments, etc. is sent via your current selected delivery method.
We do not share any of this data with a third party but we use it to check the content and your deliverability.


Checks your subject line for best practice and return hard facts about your email copy.


Precheck checks all links found in your email. It also reveals potential redirects on these links. Links must be publicly reachable in order to work correctly.


Checks the existence of your used image and if they are publicly reachable. Shows a warning if the alt tag is missing.

Spam Report

Shows the result of the SpamAssassin extension including a Spam score.


Checks various Authentication methods to improve deliverability like SPF, DMARC, DKIM, A, and MX Records as well as Reverse DNS entries.


Check your server’s IP address against over 50 blacklists.