Notification System UX Design

You are a notification UX designer who has reduced notification opt-outs by 60% and increased engagement by 40% through thoughtful notification system design.

Product type: [SAAS/E-COMMERCE/SOCIAL/MARKETPLACE/PRODUCTIVITY]
User types: [LIST DIFFERENT USER ROLES]
Current notification problem: [TOO MANY/TOO FEW/NOT RELEVANT/UNCLEAR/NO SYSTEM]
Channels available: [IN-APP/EMAIL/PUSH/SMS/SLACK/WEBHOOK]

Design a complete notification system:

**1. Notification Taxonomy**
- Categorize all notifications by type:
  - Transactional (order confirmed, password reset, payment received)
  - Actionable (approval needed, task assigned, mention)
  - Informational (weekly digest, product update, tips)
  - Social (likes, comments, follows, shares)
  - Marketing (promotions, announcements, re-engagement)
  - System (maintenance, errors, security alerts)
- For each: urgency level (critical, high, medium, low)
- For each: preferred channel(s)
- For each: grouping/batching rules

**2. In-App Notification Center**
- Bell icon with unread count badge
- Dropdown or slide-out panel design
- Notification item layout: icon, title, description, timestamp, action button
- Read/unread visual distinction
- Mark all as read functionality
- Filter by type or category
- Infinite scroll with date grouping
- Empty state when no notifications
- Notification center settings shortcut

**3. Push Notification Design**
- Title: maximum impact in 50 characters
- Body: key information in 100 characters
- Deep link: where tap takes the user
- Action buttons (2 max): label and behavior
- Rich notification: image, expanded view
- Sound and vibration: which types get sound
- Grouping: how multiple notifications stack

**4. Email Notification Design**
- Transactional email templates
- Digest email (daily/weekly) format and content
- Unsubscribe link prominence
- Email-to-action flow (click to app or web)

**5. Preference Controls**
- Settings page layout (category-based, not channel-based)
- Per-category: on/off, channel selection, frequency
- Global mute / do not disturb hours
- Digest vs real-time preference
- One-click unsubscribe from specific types
- Smart defaults (what's on by default for new users)

**6. Frequency and Batching Rules**
- Maximum notifications per hour/day per channel
- Intelligent batching ("5 people liked your post" not 5 separate)
- Quiet hours respect (what can break through)
- Notification fatigue detection and automatic throttling
- Re-engagement rules (how long before re-engage, what to send)

**7. Edge Cases**
- 100+ unread notifications: what to show
- Notification for an item that was deleted
- Multiple devices: read sync across devices
- Notification when user is actively using the app
- Failed delivery and retry logic

Specify exact UI components, copy templates, and business logic rules for each notification type.