Gmail Multi-Inbox Setup & Maintenance

Overview

Gmail's Multiple Inboxes displays up to 5 custom sections alongside the main inbox. Each section shows emails matching a search query. This skill uses a label + filter approach: label-based sections get Gmail filters that auto-label incoming mail by sender domain. The output is always a Google Apps Script the user pastes into script.google.com.

The generated script is idempotent — safe to re-run after adding or removing senders. When senders are removed from the lists, setupAll() automatically deletes the corresponding Gmail filters.

Prerequisites

This skill requires a Gmail MCP connector (e.g. search_gmail_messages) to scan the user's inbox. Gmail does not have an official MCP server — the user must have a third-party Gmail connector configured. If no Gmail connector is available, the skill can still work in a limited way: skip the scanning steps and let the user provide sender domains manually, or import from an existing script.

Configuration

The skill stores its current configuration in assets/config.json inside this skill's directory. This file tracks:

The section definitions (name, query, label)
The sender domains assigned to each label
Timestamp of last scan

Always read assets/config.json before starting. If it exists, this is a returning user — go to Update Mode. If it doesn't exist, check if the user has an existing script (see Import Existing Script). Otherwise, this is a new user — go to Initial Setup.

Import Existing Script

If the user already has a Gmail Multi-Inbox Apps Script (set up manually or from a previous run before config tracking existed), ask them to paste it. Parse the script to extract:

Sender arrays — find all var xxxSenders = [...] declarations, extract the domain lists and map each to its label name
Labels — find all createLabelIfNeeded('...') calls to identify the label names
Section config — find the __MULTI_INBOX_CONFIG__ comment block or any section query/name comments

Build assets/config.json from the parsed data and confirm the reconstructed config with the user before proceeding to Update Mode.

Initial Setup (New Users)

Step 1: Scan Gmail

Search the user's Gmail history using search_gmail_messages to build a comprehensive picture of who emails them. Run multiple queries and merge the results — the goal is to discover all non-personal sender domains.

Broad sweep (most important — do this first):

newer_than:6m — all emails from the last 6 months. Paginate through results to collect as many senders as possible.
newer_than:1m — recent emails, captures current high-frequency senders

Category-based (catches things the broad sweep may paginate past):

category:promotions — marketing, newsletters
category:updates — notifications, shipping, orders
category:social — social media notifications
category:forums — mailing lists, digests

Signal-based:

unsubscribe — anything with an unsubscribe link (broad, catches most automated mail)
from:noreply OR from:no-reply OR from:notifications OR from:info@ — automated senders

Localized subject searches (adapt based on user's language):

subject:order OR subject:invoice OR subject:receipt OR subject:shipping OR subject:confirmation
Czech: subject:objednávka OR subject:faktura OR subject:potvrzení OR subject:doručení

Aggregate results: collect all sender addresses, extract domains, group by domain, count frequency. Ignore generic providers (gmail.com, outlook.com, yahoo.com, hotmail.com, icloud.com, seznam.cz, etc.) — these are personal contacts, not automated senders.

Step 2: Suggest Categories

Based on the scan results, propose up to 5 sections. Start with these defaults and adjust based on what the scan actually found:

#	Name	Query	Label	Description
1	Important	`(is:starred OR is:important)`	(none — query-based)	Starred and important emails
2	Work	`label:work in:inbox`	`work`	Emails from the user's company domain
3	Newsletters	`label:newsletter in:inbox`	`newsletter`	Subscriptions, digests, marketing
4	Orders	`label:orders in:inbox`	`orders`	E-shops, shipping, travel, invoices
5	(available)			Suggest based on scan or leave empty

Present the proposed sections with the discovered sender domains grouped under each category. Ask the user to:

Confirm, rename, or remove sections
Move misclassified domains between categories
Add missing domains
Name the work label after their actual company if applicable
Choose label colors (suggest distinct, visually clear defaults). Only Gmail's predefined colors are allowed — see the list in Important Notes

For section 1 (Important): this is query-based, no label or filters needed.

Step 3: Generate the Apps Script

Read the template from scripts/gmail-multi-inbox-template.js in this skill's directory.

Fill in the placeholders:

__SENDER_ARRAYS__ — one var array per label-based section with the confirmed sender domains
__LABEL_CONFIGS__ — createLabelIfNeeded('labelname', { backgroundColor: '#hex', textColor: '#hex' }) calls for each label-based section. The color object is optional — if the section has a color in the config, pass it; otherwise omit the second argument. Only Gmail's predefined hex colors are allowed (see template comments).
__STALE_FILTER_CLEANUP__ — a removeStaleFilters([...]) call listing all managed label/sender pairs. This lets the script detect and delete Gmail filters whose sender was removed from the lists. Example:
```
removeStaleFilters([
  { senders: workSenders, label: 'work' },
  { senders: newsletterSenders, label: 'newsletter' }
]);
```
__FILTER_CREATION__ — for each label-based section: loop over its sender array calling createFilterIfNeeded(sender, label). Do NOT include retroLabel calls here — those go in __RETRO_LABEL__.
__RETRO_LABEL__ — for each label-based section: call retroLabel(senderArray, label). If the section has matchToAndCc in the config, pass it as { matchToAndCc: [...] }. This is placed inside the separate retroLabelAll() function.
__MULTI_INBOX_CONFIG__ — comment block listing each section's query and name for the user to enter in Gmail Settings

Save the generated script as assets/gmail-multi-inbox-setup.js inside this skill's directory.

Step 4: Save Configuration

Write assets/config.json with the full configuration:

{
  "sections": [
    { "name": "Important", "query": "(is:starred OR is:important)", "label": null },
    { "name": "Work", "query": "label:work in:inbox", "label": "work", "senders": ["companydomain.com"], "matchToAndCc": ["companydomain.com"], "color": { "backgroundColor": "#4a86e8", "textColor": "#ffffff" } },
    { "name": "Newsletters", "query": "label:newsletter in:inbox", "label": "newsletter", "senders": ["substack.com", "beehiiv.com"], "color": { "backgroundColor": "#fad165", "textColor": "#000000" } },
    { "name": "Orders", "query": "label:orders in:inbox", "label": "orders", "senders": ["amazon.com", "ups.com"], "color": { "backgroundColor": "#16a766", "textColor": "#ffffff" } }
  ],
  "lastScan": "2026-02-18"
}

Step 5: Provide Setup Instructions

Tell the user:

Part A — Run the script:

Go to script.google.com → New project → paste the script
In the sidebar, click + next to "Services" and enable Gmail API
Run setupAll() and authorize when prompted — this creates labels, updates filters, and retro-labels existing emails

Part B — Configure Multiple Inboxes manually:

The Gmail API does not expose Multiple Inboxes settings, so this part must be done by hand in Gmail.

In Gmail: Settings (⚙️) → See all settings → Inbox tab
Set Inbox type to Multiple Inboxes

For each section, enter the Search query and Section name exactly as listed in the script's header comment. Present these to the user in a clear table, e.g.:

Section	Search query	Section name
1	`is:starred OR is:important`	Starred / Important
2	`label:work in:inbox`	Work
3	`label:newsletter in:inbox`	Newsletters
4	`label:orders in:inbox`	Orders
5	(leave empty)

Set Multiple Inbox position to "Right of inbox" (recommended)
Click Save Changes

Always present the full table with the actual section values from the config — do not just say "see the script header".

Update Mode (Returning Users)

When assets/config.json exists:

Show the user their current configuration (sections + sender counts)
Ask what they want to do: scan for new senders, add specific senders manually, remove senders, modify sections, or get unsubscribe suggestions
If scanning: re-run the Gmail searches from Step 1, compare against existing sender lists, and present only new domains not yet in the config
Let the user confirm which new domains to add and to which categories
Before generating the script, compare the new sender lists against the previous assets/config.json. If any senders were removed, explicitly list them with their section names and ask the user to confirm. The generated script will delete the corresponding Gmail filters when run — make sure the user understands this. Do NOT generate the script until the user confirms the removals.
Regenerate the Apps Script with the updated sender lists and save to assets/gmail-multi-inbox-setup.js
Update assets/config.json
User pastes the updated script and re-runs setupAll() (this handles filters and retro-labeling in one go)
If any section queries or names changed, remind the user to update their Multiple Inboxes settings manually in Gmail (see Step 5, Part B from Initial Setup). Present the updated table of sections.

Unsubscribe Suggestions

When the user asks for inbox cleanup or unsubscribe suggestions:

Step 1: Identify noisy senders

Search Gmail for senders that pollute the inbox. Focus on:

High volume, low engagement — many emails, most unread. Compare from:domain.com (total) vs is:unread from:domain.com (unread) to estimate open rate.
Never replied to — from:domain.com -in:sent has the same count as from:domain.com, meaning the user never interacts with this sender.
Promotional / transactional noise — marketing emails, "we miss you" campaigns, loyalty programs, app notifications that duplicate push/in-app notifications (e.g. social media activity digests, app usage summaries, "someone liked your post").
Redundant notifications — emails that duplicate information available elsewhere: order status (check the app), shipping updates (carrier app), calendar reminders, password change confirmations, login alerts from low-risk services.

Use broad queries to discover candidates:

unsubscribe newer_than:6m — anything with an unsubscribe link in the last 6 months (widest net)
category:promotions — marketing and newsletters
category:updates — transactional notifications
category:social — social media digests and notifications
from:noreply OR from:no-reply OR from:notifications — automated senders
subject:newsletter OR subject:digest OR subject:weekly OR subject:monthly

Then for each discovered domain, measure engagement:

Total emails: from:domain.com newer_than:6m
Unread emails: is:unread from:domain.com newer_than:6m
Any replies: compare count of from:domain.com vs from:domain.com -in:sent

Exclude senders already managed in the config (they're already categorized).

Step 2: Present recommendations

Group the noisy senders into tiers:

Unsubscribe — high volume, never read, no value (e.g. marketing from a store you bought from once, app notification digests)
Consider unsubscribing — moderate volume, rarely read, value is questionable or available elsewhere
Keep but categorize — useful but noisy — suggest adding to a section in the multi-inbox config instead

For each sender, show:

Sender domain and example "From" name
Email count (last 6 months)
Estimated open rate (read vs total)
Why it's flagged (e.g. "94 emails, 2% opened", "duplicates push notifications")

Step 3: Act on user choices

Unsubscribe: the action is manual — provide the sender info so the user can unsubscribe themselves. Do NOT generate script code to delete or archive emails without explicit user approval.
Categorize: add the sender to the appropriate section in the config and regenerate the script.
Block: explain how to block in Gmail (three dots → Block "sender"). This is also manual.

Important Notes

The Gmail API cannot configure Multiple Inboxes settings. The script handles labels, filters, and retroactive labeling. The user must always configure section queries, names, and position manually in Gmail Settings → Inbox → Multiple Inboxes. Always present the full configuration table after generating or updating the script.
Emails in labeled sections also appear in the main inbox — sections are views, not separate inboxes. Adding in:inbox to section queries ensures archived mail doesn't appear in sections.
from:domain.com matches any @domain.com address and subdomains.
One filter per sender domain (no complex boolean logic in a single Gmail filter).
Check the user's email for language clues and adapt search queries accordingly.
Label colors must use Gmail's predefined hex values. Arbitrary colors will be rejected by the API. Allowed background colors (pair with #000000 or #ffffff text for contrast):
- Reds: #fb4c2f, #e66550, #cc3a21, #ac2b16, #822111, #f6c5be, #efa093
- Oranges: #ffad47, #ffbc6b, #eaa041, #cf8933, #a46a21, #ffe6c7, #ffd6a2
- Yellows: #fad165, #fcda83, #f2c960, #d5ae49, #aa8831, #fef1d1, #fce8b3
- Greens: #16a766, #44b984, #149e60, #0b804b, #076239, #b9e4d0, #89d3b2, #43d692, #68dfa9, #3dc789, #2a9c68, #1a764d, #c6f3de, #a0eac9
- Blues: #4a86e8, #6d9eeb, #3c78d8, #285bac, #1c4587, #c9daf8, #a4c2f4
- Purples: #a479e2, #b694e8, #8e63ce, #653e9b, #41236d, #e4d7f5, #d0bcf1
- Pinks: #f691b3, #f7a7c0, #e07798, #b65775, #83334c, #fcdee8, #fbc8d9
- Grays: #000000, #434343, #666666, #999999, #cccccc, #efefef, #f3f3f3, #ffffff

gmail-multi-inbox