Mail-Tester

Mail-Tester is a free, lightweight way to score an outbound email before sending it to a list. You send a test message to the address it generates and get back a score out of 10, plus specific feedback on your configuration and any issues it detects.

The report covers SPF, DKIM, DMARC records, content that might trigger spam filters, and any blacklist problems. It's simple and effective for catching basic issues before a campaign launches.