Most inbox advice tells you to build folders around topics: "Receipts", "Projects", "Newsletters". It sounds tidy until you try to file a single email and realise it could belong in three of them. Organising by who sent the mail sidesteps that, and once you group by the sender's organisation rather than each address, an Outlook inbox more or less sorts itself.
Why topic folders quietly fail
Topic folders ask for a judgement call on every message. A Stripe payout notice is a receipt, a finance item, and a Stripe thing all at once. Multiply that hesitation across a few hundred emails a week and you get the familiar outcome: a handful of folders you use and a long tail you never open.
Sender-based filing removes the judgement. Mail from your accountant goes to one place, mail from a supplier to another. You stop deciding and start scanning.
The trap of one address per rule
The obvious way to organise by sender is a rule per address: "if from news@stripe.com, move to Stripe". This breaks faster than people expect, because real organisations send from many addresses:
news@stripe.comfor product updatesreceipts@stripe.comfor payment confirmationsnotifications.stripe.comas a sending subdomain- per-customer or per-region aliases that change without warning
Each new address slips past your rule and lands back in the Inbox. You end up maintaining a growing list of near-duplicate rules, and the folder is never quite complete. Address-level rules treat one organisation as dozens of unrelated strangers.
Group by the organisation, not the address
The fix is to file by the sender's organisation domain rather than the full address. Every address above shares the registrable domain stripe.com, so all of them should land in one Stripe folder.
This is harder than it looks. You cannot take "the bit after the last dot", and you cannot take "the last two labels" either, because domains do not follow one rule:
notifications.stripe.com→ the organisation isstripe.commail.acmeenergy.co.uk→ the organisation isacmeenergy.co.uk, notco.uknews.example.energy→ the organisation isexample.energy
The correct boundary is defined by the Public Suffix List, the same dataset browsers use to decide where one site ends and another begins. It knows that .co.uk, .com and newer suffixes like .energy are public suffixes, so the organisation is the label immediately to their left.
Sortfully does exactly this. It reads the sender's address only long enough to derive the registrable domain via the Public Suffix List, then files on that domain:
news@stripe.com,receipts@stripe.comandnotifications.stripe.comall land in one Stripe folder- a supplier on
mail.acmeenergy.co.uklands in Acmeenergy, not a meaninglessco.ukbucket - you maintain one mapping per organisation, not one rule per address
A worked example
Say your inbox is full of payment-platform noise. Out of the box, domain grouping already merges every Stripe address into a single Stripe folder. But you might prefer all your payment providers together. With an override you can group several domains — stripe.com, paypal.com, wise.com — into one Payments folder, and every message from any of them, across all their subdomains and aliases, files itself there. One folder, three providers, zero per-address rules.
You can also pin a domain to an existing folder you already use, or exclude a sender you would rather leave in the Inbox.
Move or tag, your choice
Sender-based filing does not have to mean burying everything in subfolders. For each mapping you choose between two filing modes:
- Move the message into a subfolder, keeping the Inbox empty
- Tag it with a coloured category and leave it in the Inbox, so you keep a flat inbox but still see at a glance who sent what
You can mix the two freely: move the newsletters, tag the suppliers. By default a message moves only after you have read it, so nothing vanishes before you have seen it; you can switch to file-on-delivery if you prefer. Messages are moved, never deleted, and every action is reversible with undo.
Setting it up in Outlook
The flow is deliberately low-commitment:
- Sign in with your Microsoft account (work, school, or personal Outlook.com).
- Sortfully scans your existing folders and rules, reading metadata only, and previews the folders it would create before touching anything.
- Tune the mapping or accept the sensible defaults.
- New mail then files itself automatically.
If you have years of backlog, an optional cleanup pass works through it in rate-limited chunks rather than all at once. For a fuller walkthrough of the automation side, see automatically sort Outlook emails into folders.
What it does not read
Filing by sender needs only routing information, never the contents of your mail. Sortfully is content-blind: it never reads your mail bodies or attachments. It reads the sender address transiently to derive the domain, plus basic metadata like folder, received time and read state. There is no AI involved; the rules are deterministic — your overrides first, then the Public Suffix List. That is the whole mechanism.
Worth a try
If your Outlook inbox has outgrown topic folders and address-level rules, organising by the sender's organisation is the calm middle ground: precise enough to be useful, automatic enough to stay that way. Sortfully is in a private, invite-only beta — you can join the waitlist and we'll email you when it opens.