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B2B Inbox Engine Optimization IEO: Win Triage and Scheduling After Perplexity Email Assistant
AI agents now read B2B email first. Use Inbox Engine Optimization to declare intent in the subject, lead with a short TLDR, expose ISO time windows, attach an ICS option set, keep one executable CTA, and add machine readable snippets that assistants can act on.
Vicky
Sep 24, 2025
Context
Perplexity Email Assistant launched on September 23, 2025, which means AI agents will often be the first readers of your outreach. Treat email like SEO for inboxes so assistants can classify, summarize, and execute your ask quickly. See the official announcement for details on capabilities in the Perplexity Email Assistant launch. For broader AI surface strategy, pair this with our Private Graph AEO playbook and the Session Engine Optimization guide.
1) Subject that states intent and entities
Use short tokens the assistant can parse. Put high signal first.
- Pattern: [Intent:Meeting][Duration:15m][Company:Acme][Topic:Q4 pilot][Due:2025-09-30]
- Alternates: [Intent:Renewal][Contract:CR-2024-1189][ARR:120k][Due:2025-10-15]
Rules
- Keep under 90 characters. No filler words. No emojis.
- Use key:value tokens in square brackets. CamelCase entities if needed.
- Include one triage date such as Due, Renewal, Ship, or Close.
2) Above the fold body
Assistants skim the first 300 characters. Order matters.
- Salutation
- TLDR: one sentence with value, action, and time cost
- Proof: one datapoint or named peer
- Availability: ISO 8601 windows that are easy to book
- Single CTA: executable in one step
Template
- TLDR: We can reduce invoice matching time by 40 percent for Acme with a 15 minute pilot this week.
- Proof: Atlas cut manual review from 5 hours to 3 hours per batch.
- Availability: 2025-09-29T14:00-16:30-04:00 or 2025-09-30T10:00-12:00-04:00.
- CTA: Reply 1 to book the first window, 2 for the second, or 3 to propose another.
3) Machine readable footer block
Place a compact, human readable block at the end. Assistants will parse keys reliably. Keep names stable and use ISO formats.
INTENT=MEETING_REQUEST
COMPANY=Acme Corp
CONTACT_NAME=Priya Shah
THREAD_KEY=ACME_Q4_PILOT
DURATION=PT15M
AVAIL_WINDOWS=[{"start":"2025-09-29T14:00:00-04:00","end":"2025-09-29T16:30:00-04:00"},{"start":"2025-09-30T10:00:00-04:00","end":"2025-09-30T12:00:00-04:00"}]
CTA=Reply 1 or 2 or 3
ORDER_ID=PO-45001933
CONTRACT_REF=CR-2024-1189
RENEWAL_DATE=2025-10-15
VALUE_ESTIMATE_USD=120000
DATA_CLASS=Business_contact_only
4) ICS option set attachment
Attach one .ics with multiple tentative options so assistants can offer one click accept. Use METHOD:REQUEST and 3 VEVENTs with STATUS:TENTATIVE. Keep durations identical. Conform to the RFC 5545 iCalendar spec.
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//YourCo//IEO//EN
METHOD:REQUEST
BEGIN:VEVENT
UID:opt1-20250929-1800Z@yourco
SUMMARY:Acme x YourCo intro 15m
DTSTAMP:20250924T150000Z
DTSTART:20250929T180000Z
DTEND:20250929T181500Z
STATUS:TENTATIVE
END:VEVENT
BEGIN:VEVENT
UID:opt2-20250929-2000Z@yourco
SUMMARY:Acme x YourCo intro 15m
DTSTAMP:20250924T150000Z
DTSTART:20250929T200000Z
DTEND:20250929T201500Z
STATUS:TENTATIVE
END:VEVENT
BEGIN:VEVENT
UID:opt3-20250930-1400Z@yourco
SUMMARY:Acme x YourCo intro 15m
DTSTAMP:20250924T150000Z
DTSTART:20250930T140000Z
DTEND:20250930T141500Z
STATUS:TENTATIVE
END:VEVENT
END:VCALENDAR
Notes
- Use Z times or include TZID explicitly. Keep all options 15 minutes for simple suggestions.
- File name pattern: acme-intro-options-2025-09.ics
5) Offer reply scaffolds that agents can surface
Add a short list that maps to canned replies. Keep it visible but unobtrusive.
Reply-Options
1 Confirm 2025-09-29T14:00-04:00
2 Confirm 2025-09-29T16:00-04:00
3 Confirm 2025-09-30T10:00-04:00
4 Ask for more info on security review
5 Not a fit, please remove
6) Keep one CTA and make it executable
Good
- Reply 1 to confirm a time
- Or click Accept on any attached invite
Avoid
- Multiple asks like book a demo, download a whitepaper, and introduce someone
7) Snippets that boost triage and routing
Include only if relevant and correct.
- Account_ID=ACME-4421
- Opportunity_Stage=Evaluate
- Region=NA
- Product_Tier=Enterprise
- Security_Doc=On_request
- Renewal_Date=2025-10-15
- Ticket_ID=INC-128377
- SOW_Version=v3.2
8) Example email skeleton
Subject: [Intent:Meeting][Duration:15m][Company:Acme][Topic:AP automation][Due:2025-09-30]
Hi Priya,
TLDR: We cut invoice matching by 40 percent for peers and can show a 15 minute pilot for Acme this week.
Proof: Atlas and Northbeam reduced manual review by 2 hours per batch.
Availability: 2025-09-29T14:00-16:30-04:00 or 2025-09-30T10:00-12:00-04:00.
CTA: Reply 1 or 2 to confirm. I attached a calendar options file.
Thanks,
Jordan
INTENT=MEETING_REQUEST
COMPANY=Acme Corp
THREAD_KEY=ACME_Q4_PILOT
DURATION=PT15M
AVAIL_WINDOWS=[{"start":"2025-09-29T14:00:00-04:00","end":"2025-09-29T16:30:00-04:00"},{"start":"2025-09-30T10:00:00-04:00","end":"2025-09-30T12:00:00-04:00"}]
CTA=Reply 1 or 2
CONTRACT_REF=CR-2024-1189
RENEWAL_DATE=2025-10-15
9) Formatting rules for assistant friendliness
- Prefer text first. If you send HTML, include a plain text version.
- Use short sentences. Keep the first paragraph under 300 characters.
- Quantify benefits and time costs.
- Avoid trackers and heavy CSS. They reduce deliverability and trust.
- Keep capitalization normal. Avoid all caps in subjects.
10) QA checklist before sending
- Subject contains [Intent] and at least one date or identifier.
- First line is a clear TLDR.
- ISO 8601 availability windows are present and realistic.
- One CTA only with no competing links or asks.
- ICS with 2 to 3 tentative options attached.
- Machine readable footer with stable keys, IDs, and dates.
- Company and contact names are correct and consistent.
- Privacy checked. No sensitive data without consent.
11) How to measure IEO performance
Track assistant surfaces and outcomes, not just open rate.
- Summarized in inbox yes or no
- Suggested reply appeared yes or no
- One click calendar accept rate
- Time to meeting booked
- Reply code distribution 1 to 5
12) Iterate fast
Run A B tests on subject tokens, TLDR phrasing, and window count. Keep all other elements constant for one week. Promote the winners. For adjacent playbooks on AI surfaces, see the Reddit Answers AEO playbook.
Bottom line
Say what the assistant needs to know in the places it looks first. Put intent in the subject, a TLDR in the first line, ISO windows in the body, one executable CTA, an ICS option set, and clean snippets. That is how you win triage, summaries, scheduling, and suggested replies.