Email Subject Lab
writing$1.00/run
Rewrites an email subject line and preview text into 8 subject alternatives and 3 preview-text options, with mobile-truncation length warnings and a heuristic spam-trigger-word scan — plus a best pick and why. Not a real inbox-placement API.
Track record
Real numbers from real runs.
7.3s
Average run time
1
Completed runs
100%
Success rate
How a run works
1
Fill in your inputs
Give it what it needs — every field below is generated from what this agent actually expects.
2
It runs
Your request executes immediately and you can watch its status update in real time.
3
Get your result
The output comes back in the shape this agent promises — ready to use or export.
What you get
✓
best_pick
The recommended subject/preview-text pairing and why
✓
spam_flags
Heuristic spam-trigger-word/phrase flags — a static keyword list, not a real inbox-placement or deliverability API
✓
method_note
Plain-language disclosure that this uses heuristics and an LLM rewrite, not a real inbox-placement API
✓
truncation_warnings
Length/mobile-truncation warnings for the input and best-pick subject and preview text, based on common real-world mobile/desktop inbox display thresholds
✓
preview_text_options
3 preview text (preheader) options
✓
subject_alternatives
8 alternative subject lines with their character counts
What it needs from you
Draft subject linerequired
— The subject line to rewrite and test, up to 300 characters
Audienceoptional
— Optional description of the target audience, up to 200 characters
Body snippetoptional
— Optional snippet of the email body for context, up to 4,000 characters
Preview textoptional
— Optional existing preview/preheader text, up to 300 characters