deliverability-optimization

name	deliverability-optimization
description	Email deliverability optimization skill used by the Editor-in-Chief and analyst agents. Provides spam filter avoidance, technical authentication, content filtering rules, and list hygiene management methodologies. Use for 'deliverability,' 'spam filters,' 'email authentication,' 'send optimization,' and similar requests.

Deliverability Optimization — Email Deliverability Optimization Methodology

Technical deliverability expertise used by the editor-in-chief and analyst agents when designing final edits and send strategies.

Why Deliverability Matters

No matter how perfect your newsletter is, if it doesn't reach the inbox, all effort is wasted. On average, 15–20% of emails land in spam folders or promotional tabs.

Spam Filter Trigger Avoidance Guide

Subject Line Spam Trigger Words

Risk Level	Word/Pattern	Alternative
High	Free, FREE, 100% off, Winner	"Complimentary," "Gift," "Special offer"
High	!!!, ???, ALL CAPS	One exclamation max, sentence case
Medium	Act now, Urgent, Deadline	"By this week," "Limited time"
Medium	Click here, Click now	"Check it out," "Take a look"
Low	Re:, Fwd: (fake reply/forward)	Absolutely prohibited — destroys trust

Body Content Filtering Rules

1. Image-to-text ratio: Keep images at 40% or less, text at 60% or more
2. Link count: 5–7 per email is optimal; 15+ risks spam classification
3. Shortened URLs: Shortened URLs (bit.ly, etc.) trigger spam filters — use original URLs
4. HTML code quality: No broken tags or excessive inline styles
5. Unsubscribe link: Must be clearly included at the bottom (legal obligation + spam prevention)

Sender Reputation Management

Factor	Optimal State	Management Method
Bounce Rate	Below 2%	Remove hard bounces immediately, soft bounces after 3
Spam Complaint Rate	Below 0.01%	Maintain content quality, make unsubscribing easy
Authentication	SPF + DKIM + DMARC configured	Coordinate with domain administrator
Dedicated IP	When sending 100K+/month	Shared IPs are affected by others' reputation
IP Warm-up	Gradual increase over 2–4 weeks for new IPs	Day 1: 50 emails → double daily → target volume

Email Client Rendering Checks

Rendering issues that must be verified during newsletter editing:

Client	Considerations
Gmail	Prevent Promotions tab classification — reduce images, increase text, use personal tone
Outlook	Limited CSS support — avoid complex layouts, use table-based layouts
Apple Mail	Dark mode support — use transparent background images, test color inversion
All Mobile	Single-column layout, buttons minimum 44x44px, font 14px+

Gmail Promotions Tab Avoidance Strategy

1. Personal tone: "Hi [Name]" — minimize marketing-speak
2. Minimize images: Text-centric, limit to 1–2 images
3. Minimize links: Keep to 2–3 essential links only
4. Encourage replies: "Reply to this email" — signals two-way communication
5. Sender name: Personal name over brand name (e.g., "Jane from [Newsletter Name]")

Legal Compliance Checklist

Legal requirements that must be verified when publishing a newsletter:

CAN-SPAM (US)

• Physical mailing address included
• Unsubscribe processed within 10 business days
• No deceptive subject lines

GDPR (EU)

• Explicit consent (no pre-checked boxes)
• Data processing purpose stated
• Data deletion request handling system
• Privacy policy link

CASL (Canada)

• Express or implied consent obtained
• Sender identification included
• Unsubscribe mechanism provided

Editor-in-Chief's Pre-Send Checklist

#	Item	Check
1	No spam trigger words in subject line	[ ]
2	Preheader text configured	[ ]
3	All links verified working	[ ]
4	Image alt text entered	[ ]
5	Mobile rendering tested	[ ]
6	Unsubscribe link working	[ ]
7	Sender information accurate	[ ]
8	A/B test setup confirmed	[ ]
9	Send time optimized per segment	[ ]
10	Test send → receipt confirmed	[ ]