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Rather than rank seven tools in a row and call one the winner, this guide scores each AI email assistant against six buying criteria. Read the criteria that matter to you, skip the rest, and the right pick falls out on its own.
The best AI email assistant is the one that fixes your particular bottleneck, and the six criteria below tell you which that is. Pidgy scores highest overall because it is the only tool here that ranks Outlook and Gmail as one inbox and then chases the threads that stall. Fyxer wins if you want meeting notes with your drafts, Superhuman if you want speed, Shortwave if you live in Gmail, Serif if voice-accurate drafts are the whole point, Kinso if your messages arrive on five apps, and SaneBox if you only want cheap filtering.
An AI email assistant plugs into an Outlook or Gmail account, reads what arrives, and takes over part of the handling. Depending on the tool that means deciding what needs you, writing a reply that sounds like you, condensing a long thread, or noticing that someone never wrote back. A good one lowers the number of emails you personally touch in a day; a mediocre one just moves them into folders.
Four of the seven sit on top of your existing account. Two replace your email client outright, and one pulls Gmail into a feed with your chat apps.
Pidgy, Fyxer, Serif and SaneBox all work as a layer, so you keep Outlook or Gmail and the assistant works behind it. Pidgy goes a step further and reads both providers as one inbox, which matters if your firm runs Microsoft 365 but half your clients write to a Google address. Superhuman and Shortwave are replacement clients. Superhuman supports both providers but expects you to learn its keyboard shortcuts, while Shortwave is Gmail only. Kinso connects to Gmail and then adds Slack, WhatsApp, LinkedIn and Instagram around it, with no Outlook support. The practical rule is that a layer costs you an afternoon to trial and nothing to leave; a replacement client costs you a habit.
Only Pidgy hands you a short ranked list of the emails that need a reply from you today. The others sort, bundle or filter.
Sorting is not useless. Fyxer's fixed categories and SaneBox's low-priority folder both make an inbox quieter, and Shortwave's thread bundling tidies Gmail considerably. But a tidy inbox with 90 messages in it is still 90 decisions. Ranking removes the decisions. Pidgy reads everything across Outlook and Gmail, decides which handful genuinely need you, and puts those at the top with the rest grouped by project underneath. It also rolls the whole picture into a single Inbox Health score, so you can tell at a glance whether Monday is under control or not. Superhuman offers AI triage inside its client, and Kinso opens with a morning briefing across all its channels, which is closer to ranking than filing but is spread across five apps rather than focused on email.
Every tool here will write a reply. The useful question is how much of it you have to rewrite before you can send it.
Serif exists almost entirely for this criterion. It pre-drafts replies in your own voice inside Gmail or Outlook, and does little else, which is why its scope is narrow. Fyxer learns from your sent history and drafts from that. Pidgy drafts in your voice as well and adds four selectable tones, so the same reply can go out brisk to a colleague or careful to a client, and you pick which before sending. Superhuman has AI drafts built into its compose window, and Shortwave's Ghostwriter does the same for Gmail. Kinso drafts too, across every channel it connects. SaneBox does not draft at all; it filters and stops there.
Pidgy is the only assistant on this list that chases stalled follow-ups by itself. Every other tool stops once the draft is written.
A proposal goes out on Tuesday. By the following Monday there is no answer, and the thread has slid two screens down. This is the point where most AI email assistants have already done their job and left. Pidgy tracks the threads that are waiting on someone else, drafts the nudge when a reply is overdue, and puts it in front of you to send. Fyxer's notetaker will write up a meeting and draft the follow-up email that comes out of it, which is useful, but it is a one-time draft rather than ongoing chasing. If lost threads are your real problem, this criterion alone decides the purchase.
Monthly costs run from about $7 to about $100. The gap between headline price and real price is where to look.
SaneBox is the cheapest at roughly $7 a month, and it does the least. Shortwave has a free tier, then paid plans from about $14 up to about $100 a month. Fyxer is about $22.50 a month, but that is on annual billing and there can be volume overage fees on top. Superhuman is about $30 a month and is now part of Grammarly. Serif makes a point of transparent monthly pricing with no overage fees. Kinso's pricing is not something we have verified, so it is left out of the comparison. Pidgy is open to everyone and starts with a 7-day free trial, no credit card needed. Read the billing period and the overage clause before you compare headline numbers.
For client-confidential work, the hosting region and the training policy are part of the feature list, not the small print.
Pidgy is hosted in the EU, never uses your email to train any model, will provide a DPA on request, and never sends a message without your click. You can, over time, set rules for routine items such as confirming receipt of a document, but the default is that nothing leaves without you. Serif also states GDPR handling. For the others, check the vendor's own data page; the answers differ and they change. If you are a lawyer, accountant, auditor or advisor, ask this question first and only then look at the drafting quality.
| Assistant | Layer or client | Ranks | Chases follow-ups | Monthly price |
|---|---|---|---|---|
| Pidgy | Layer, Outlook and Gmail as one | Yes, plus Inbox Health score | Yes | 7-day free trial |
| Fyxer | Layer, Outlook and Gmail | Fixed categories | No | About $22.50, annual |
| Superhuman | Replacement client | AI triage | No | About $30 |
| Shortwave | Replacement client, Gmail only | Bundles threads | No | Free, then $14 to $100 |
| Serif | Layer, Outlook and Gmail | No, drafting only | No | Monthly, no overage fees |
| Kinso | Unified feed, Gmail plus chat apps | Morning briefing | No | Not verified |
| SaneBox | Layer, Outlook and Gmail | Filters low priority | No | About $7 |
One paragraph each, with the reason you would choose it and the reason you might not.
Pidgy reads Outlook and Gmail together, ranks the few messages that need you, drafts in your voice with four tones, and chases follow-ups that go quiet. Email, documents and tasks are grouped into projects, and one Inbox Health score summarises the lot. A built-in assistant answers questions about your inbox, with voice on the way. EU-hosted, no training on your mail, no send without your click.
You might not choose it if you need a meeting notetaker.
Fyxer sorts your inbox into categories, drafts replies from your sent history, and sends a notetaker into your calls that writes the follow-up afterwards. It works in Outlook and Gmail.
You might not choose it because billing is annual at about $22.50 a month, overage fees are possible, and the categories cannot be changed.
Superhuman is a keyboard-first client where every action completes in under 100 milliseconds, with AI drafting and triage built in. It is now part of the Grammarly suite.
You might not choose it because it replaces your client, has a learning curve, and costs about $30 a month.
Shortwave rebuilds Gmail as a chat-like interface with thread bundling, Ghostwriter drafts and the best AI search of the group. A free tier exists, and paid plans run from about $14 to $100 a month.
You might not choose it because it is Gmail only and it replaces your client rather than sitting behind it.
Serif pre-drafts replies in your own voice inside the Gmail or Outlook inbox you already use, with transparent monthly pricing, no overage fees and GDPR handling.
You might not choose it because it stops at drafting; there is no ranking, project view or follow-up chasing.
Kinso is a universal inbox that pulls email, Slack, WhatsApp, LinkedIn and Instagram into one feed, opens the day with a briefing, drafts replies and includes a voice assistant. It connects to Gmail.
You might not choose it because there is no Outlook support and its email handling is broad rather than deep.
SaneBox moves low-priority mail out of the way without changing your client, and has done so reliably for years. It costs about $7 a month.
You might not choose it because filtering is all it does. No drafts, no ranking by what needs you, no chasing.
Six criteria, one tool that scores on all of them.
Try Pidgy for freeHead-to-head pages and alternative lists from the Pidgy team.
Pidgy ranks Outlook and Gmail as one inbox, drafts in your voice, and chases what stalls. Start your free trial below.
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