What email content triggers spam filters?
ALL CAPS in subject lines, spam trigger words (FREE, GUARANTEE, ACT NOW), red text, too many images, tiny fonts, attachments, no plain text version, and low text-to-image ratio. Use clear subjects, personalize with the recipient's name, include plain text, and link to content instead of attaching.
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More FAQs in Amazon SES Email Deliverability Best Practices Avoiding Spam Folders
Common causes: missing SPF/DKIM/DMARC records, high bounce or complaint rate, new domain without warmup, spam trigger words in content, no plain text version, inconsistent from address, or bad sender reputation. Use mail-tester.com to diagnose.
Start with 50 emails/day in week 1, 200/day in week 2, 500/day in week 3, 1000/day in week 4, and continue increasing. This builds sender reputation gradually. Sudden spikes of thousands of emails trigger spam filters on new domains.
Bounce rate should be below 5%. Complaint rate (users marking as spam) should be below 0.1%. If rates exceed these, email providers may block or throttle your domain. Set up SNS notifications to track bounces and complaints, and never send to bounced addresses.
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