Tags
What are tags?
Tags are labels you can attach to emails to organize and categorize them. They help you:
- Track campaigns: Group emails by marketing campaigns or newsletters
- Organize by department: Separate transactional emails by department (billing, support, etc.)
- Filter messages: Quickly find specific types of emails in your dashboard
- Analyze performance: Compare metrics across different email categories
Adding tags to emails
Via API
Add a tag field to your API request:
Via SMTP
When using SMTP, add the X-LM-Tag header to your email:
Tag format requirements
| Constraint | Value |
|---|---|
| Max length | 255 characters |
| Allowed characters | a-z, A-Z, 0-9, _, -, space |
| Pattern | ^[a-zA-Z0-9_-]+(?:\s[a-zA-Z0-9_-]+)*$ |
Spaces are allowed between words but not at the beginning or end of a tag.
Valid examples: newsletter, order-confirmation, Order Confirmation, invoice_2024
Invalid examples: Newsletter (leading space), invoice@2024 (@ not allowed), order.confirmation (. not allowed)
Naming conventions
Use consistent patterns to keep tags organized and machine-readable:
- Use prefixes by category:
billing-invoice,support-ticket,marketing-promo - Include dates for campaigns:
newsletter-2025-01,black-friday-2024 - Keep tags lowercase: Makes filtering and analytics queries simpler
Filtering messages
Filter by specific tag
Retrieve all messages with a specific tag:
Team isolation
Tags are isolated to your team:
- Each team has its own set of tags
- Tags with the same name can exist across different teams
- Switching teams shows only that team's tags
Tags are created automatically when you first use them. There's no need to pre-create tags before sending emails.
Tags are included in webhook event payloads for all message events. Use them to correlate webhook data with your systems.
Limitations
- One tag per message: Each email can have only one tag
- No tag updates: Once an email is sent, its tag cannot be changed
- Automatic cleanup: Unused tags (with no associated messages) may be removed during message cleanup
Related
- Webhook events — Tags are included in all message event payloads
- Metadata — Attach custom key-value data to messages