You can use mail-tester.com Show archive.org snapshot to check your application's e-mails for issues that might cause e-mails to be classified as spam.
They provide a one-time e-mail addresses that you can use to sign up etc. You can then check for scoring results of SpamAssassin and other potential issues.
You don't need to hit 10/10. Something around 9/10 is perfectly fine.
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