Every Fastmail account. One inbox. And every mail you ever got, found in a second.
Opensolr Mail is a free, open source Android client for people who live in more than one Fastmail account. One unified inbox, conversations in threads, notifications you can act on, search, contacts, your Fastmail Notes and calendars, all with a Fastmail account alone — and, if you connect Opensolr, a search that understands what you mean and reads the text inside your attachments.
Ask your mail a question. The AI answer reads the mails your search found and tells you what they say: the amount on the March invoice, the day the contract was signed, the link to pay. It will not cure anything or book your holiday, and it will not quote you a price from a shop you have never heard of. It reads your mail, and only your mail.
Free and open source under the MIT license. Android 8.0 or newer and a Fastmail account: that is all it needs. No Opensolr account is needed for anything — inbox, notifications, search, contacts, notes and calendars all work with Fastmail alone. Search by meaning, AI answers and instant push are an optional extra in your own Opensolr Index, on the free Opensolr account, no card, no expiry. Create one only if you want them.
No Opensolr account needed. For anything.
Nothing in the app waits for an Opensolr account, and nothing is locked behind one. Sign in to Fastmail and every screen works. Opensolr is an extra you can add, or never add, whenever you like.
| Feature | With Fastmail alone | With an Opensolr account too |
|---|---|---|
| Unified inbox | Every account, every folder, threads, swipes, bulk actions | The same |
| Writing | Reading, writing, replying, forwarding, attachments | The same |
| Notifications | Mark as read, Delete, Reply all; new mail checked every 15 minutes | New mail pushed the moment it arrives |
| Search | Fastmail’s own classic search by words, newest first | Words and meaning, AI answers, text inside attachments and pictures, filters, grouping |
| Chat with your mail | Not available | Ask your mail in your own words, in a conversation, across all your folders, in your language, with the mails the answer came from linked, and commands for times, rates and VAT |
| Contacts | Your Fastmail address books and the phone’s contacts, with Compose on each | Plus everyone you ever wrote with |
| Notes & calendars | Fastmail Notes, calendars in the phone’s calendar | The same |
| Updates | From GitHub, checked daily, or from Google Play | The same |
On a real phone, with real mail.
Three Fastmail accounts, years of mail, and the answers it gave. Invoice numbers, card digits, addresses and other people’s names are blurred.
Six problems. One app.
Opensolr Mail was written for one kind of person: the one with a personal Fastmail, a work Fastmail and two more domains on the side, who is tired of switching between them and of not finding the mail that was definitely there.
1 · Several Fastmail accounts, one inbox
Work, personal, the side project, the family domain. Every inbox, every Sent and Drafts folder, every Archive, all in one list, instead of switching from one account to the next and missing the mail that landed in the other one.
2 · Mail you can actually find
Search works with Fastmail alone, by words. Connect Opensolr and you type what you remember, not the exact words: search matches the words and the meaning together, so “the quote for the new roof” finds the mail that said “estimate for replacing the shingles”. An AI answer on top reads your own results and tells you what they say.
3 · The invoice inside the PDF
The number you remember is printed inside an attachment, not in the mail. With an Opensolr account, Opensolr’s servers read the text of PDFs, Office documents and pictures straight from Fastmail, the pictures inside a scanned PDF included, so a search finds the invoice by the number, the total or the name printed in it. Your phone never downloads a thing for it.
4 · Push you can act on
New mail shows up with exactly three buttons, every 15 minutes with Fastmail alone and the moment it arrives with Opensolr: Mark as read, Delete and Reply all, typed right in the notification. Most mail never needs the app opened at all.
5 · Fastmail, done natively
Your Fastmail password and two-factor code, on Fastmail’s own page. No IMAP settings, no app passwords. Your Fastmail Notes are in the app, and your Fastmail calendars sync into the phone’s calendar.
6 · Nothing you have to take on trust
Every line is on GitHub under the MIT licence. Your search lives in an Opensolr Index that belongs to your account, and the app runs without an Opensolr account at all: inbox, search, contacts, notes and calendars.
Your accounts go in. One inbox comes out.
Sign in to Fastmail and the whole app is there: inbox, search, contacts, notes, calendars. Only if you want AI search, connect an Opensolr account and every message is indexed in the background, newest first, into an index that belongs to you. Nothing to configure on either side.
- Sign in to FastmailFastmail’s own sign-in page opens in your browser, with your password and your two-factor code. The app never sees your password and needs no app password. Add as many accounts as you have.
- Read, reply, get on with your dayThe unified inbox fills at once. New mail arrives with a notification you can answer from.
- Optional: connect Opensolr for AI searchSkip it and the app works just the same. One more sign-in, in the browser. The app creates your mail index, reads your whole history into it in the background, and keeps it in step with every new, moved or deleted message.
- SearchWith Fastmail alone, by words, newest first. With Opensolr, type what you remember: words and meaning are matched together, an AI answer sums up what your results say, and filters narrow it down.
“What did the accountant say about the March invoice?”
With an Opensolr account, ask it like that. The same hybrid search that runs Opensolr’s site search matches your words and what they mean, across every account at once, and an AI answer reads the best results and tells you. Your mail is searched in your own Opensolr Index, never in a shared one.
What it finds
Words and meaning, in the mail and in what is attached to it.
- By meaning. “flight tickets” finds the boarding pass that never used the word ticket.
- By the exact word. A code, an order number, a name: switch AI off and the search matches words only.
- Inside attachments. PDFs, page by page and with the pictures in them read by OCR, Word, Excel, PowerPoint, OpenDocument, RTF and pictures are read into text on Opensolr’s servers, never through your phone. Archives are never opened.
- Dates in words. “last month”, “yesterday”, “2 weeks ago” or “march 2025”, in seven languages, keep only the mail from those days.
- Operators.
+wordmust be there,-wordmust not,"a phrase"stays together; the ? in the search box explains them. - Fresh first. The Fresh switch pushes recent mail up hard, for when you know it was last week.
How you narrow it down
Filters and groups built from your own mail.
- Suggestions as you type. After two characters, the people and conversations that fit show up under the box, before you search.
- Best matches first. The results that clearly fit sit on top; the rest waits, folded, under Also similar.
- From and To, each person with their address, one line per address.
- Company, account, folder, year, weekday and the type of attachment.
- Any two days on a calendar, and switches for unread, flagged, answered, with attachments and with attachment text.
- Your balance. A slider in Settings decides how much meaning and how much exact words count, and Lexical matching, Flexible, Balanced or Strict, how many of your words a message must contain.
- Then all of it at once. One tick selects every result the search found; move them to any folder, to Trash or to Junk, each message into its own mailbox, thousands in a few seconds.
Suggestions as you type
Type two characters and pause: up to 4 people whose name or address contains them, the ones with the most mail first, and up to 6 conversations whose subject, people or attachment names start with your words, newest first.
Tap a person to search their name, or a conversation to open it. Only with search in your Opensolr Index. How suggestions work.
It reads your results. It does not make things up for fun.
No miracle, no magic, no cure for anything. After a search, one tap and the AI answer reads the mails at the top of your results and tells you what they say, in a few lines, with the dates, the amounts and the links taken from those mails. Handy when the answer is spread over a thread of twelve replies and two invoices.
What it reads
Your best results, and nothing else.
- The results on your screen. The first ten, and only those that score at least three quarters as well as the best; a weak match is left out rather than padded in.
- Whole conversations. When a result is part of a thread, every message of it is read in order, each without the quoted history underneath, so the same paragraph is not read five times.
- Who, when, what. From, To, the date, the subject and the words of each message, as plain text.
- Attachments, by name and by text. It knows a contract or an invoice is attached, and reads the first thousand words the app read out of it (documents and pictures), so the total or the address printed inside counts too.
How you steer it
The search decides what it reads; you decide how it writes.
- Operators first.
+amazonkeeps only the mails that say it, so the answer is about Amazon and nothing else. - Your own instructions. “Short, focused, lists only where they help”, written once, kept on the phone, added to every answer and never to the search.
- Regenerate or close. Ask again over the same results, or put it away. A new search stops the old answer at once.
- Off when you want it off. Switch AI off and the search goes by exact words only.
Ask your mail. In your own words.
With an Opensolr account and AI in your plan, the Chat button next to Search opens a chat with your own mail. Ask who wrote, what was agreed, an amount, a date. The assistant decides by itself how to look through your Opensolr Index, the way you would use a search engine, and answers word by word, in the language you write in, with every mail it used linked by its subject, its date, its sender and its folder. Its sources sit under the answer as small pills: a tap opens the conversation or the file.
How it looks
A different way for a different question.
- By meaning, for questions and topics: words and meaning together.
- By the exact words, for names, addresses, companies, order, invoice and tracking numbers, codes and quoted phrases.
- The latest one. “The last invoice from …” searches by words and meaning with recent mail boosted, never simply the newest mail in your inbox; “and the one before it?” runs the same search again, cut at that mail’s date.
- Lists by sender, period, unread, flagged or with attachments, newest first, and one folder when you name it: “what came today”.
- Whole conversations, when the answer needs more than the search returned, with the text read from their attachments.
- Periods in words, “yesterday”, “the last 7 days”, “in March”, “since May”, counted in your phone’s time zone.
- Names written another way. A sender written differently is looked for among the words, and an exact-word search that finds nothing is run again by meaning.
What else it does
Small things you would otherwise leave the app for.
- Commands, answered at once. Start with
/:/time,/rate,/vat,/vatcheck,/distance,/place,/postal,/ip,/language,/translate,/search. Typing/lists them; the ? explains each one. - A conversation. The 20 earlier messages go with each question, so “and in October?”, “it” and “that mail” are understood, and a correction is taken as true and the mail read again.
- All your folders. Every search looks in all of them, Trash and Junk included, for the accounts signed in on this phone; your own addresses are known as yours.
- Your language. The answer is in the language you write in, whatever the language of the mail.
- Your settings. Your AI instructions, your balance between words and meaning, and your lexical matching.
- Kept on the phone, also after closing the app, until New chat clears it; after 50 questions a new chat starts on its own.
- Light on your plan. Exact-word searches that find mail, lists, conversations, lookups and most commands use no AI requests.
A mail client, compact and quick.
Flat, dense, no wasted space. Every list remembers where you were, every fold stays folded, and every action answers with a small tap you can feel.
One inbox for every account
All Inboxes, All Drafts, All Sent, All Archive, All Junk, All Trash and Flagged, across every Fastmail account you add, with each account’s own folders under it. With more than one account, a thin coloured stripe on each message tells you which one it came to.
Conversations in threads
A reply sits with the mail it answers. Open a conversation and every message is there, each one opening with a tap, with Reply, Reply all, Forward and Copy on each. Tap a name or an address to copy it; save any attachment to the phone.
Grouped the way you think
The list is grouped by day, by default, or by month, sender, company or account. Every group folds, the app remembers which ones you folded, and one button folds or opens them all.
Swipe, select, done
Swipe left to delete, right to flag. Press and hold to select several conversations and mark them read, flag, archive or delete them together. In search, one tick selects everything the search found. Every action gives a small tap back you can feel.
Mark all as read, empty the bin
One button marks a whole inbox as read, or all of them at once. Press and hold Trash or Junk and empty it for good, on Fastmail too, after a second tap to be sure.
Notifications with three buttons
Mark as read, Delete, Reply all. The reply is typed in the notification and goes to everyone on the thread. Nothing else, on purpose.
Search that remembers where you were
Your query, your filters, your grouping and where you had scrolled to stay exactly as you left them, for the whole time the app is open. A fast scroller with a tap at every date you pass gets you through years of mail in a second.
Contacts, from everywhere
Everyone you can write to in one list: your Fastmail address books, the phone’s contacts if you allow it, and, with Opensolr, everyone from your mail. One card per person, A to Z, with addresses, phones and postal addresses, a search box and Compose on each card. The same people are suggested as you type in To, Cc and Bcc. No Opensolr account needed.
Fastmail Notes
The notes you keep in Fastmail, read, written, pinned and deleted in the app.
Your calendars, in your calendar
Each account’s Fastmail calendars sync both ways into Android’s calendar, so Google Calendar, or any calendar app, shows and edits them. Switch it on or off per account.
Seven languages
English, Deutsch, Français, Español, Română, 日本語 and 中文, following the phone or chosen in Settings.
Updates itself
Once a day the app looks for a new release on GitHub. When there is one, it downloads it, checks that it carries the same signature and is really newer, and hands it to Android’s installer. A copy installed from Google Play is updated by Google Play.
Between Fastmail, your phone and your own index.
Where your mail goes
And only there.
- Fastmail keeps your mail, as it always did. The app talks to it directly.
- The phone keeps a local copy for the inbox, so lists open at once.
- Your Opensolr Index, only if you connect one, holds the text of your messages and of their attachments for search, the attachments read on Opensolr’s servers straight from Fastmail, never through your phone. It is yours: see it, back it up or empty it from the Opensolr control panel, or from the Opensolr app.
- Your contacts: Fastmail address books are read from Fastmail; the phone’s contacts, only if you allow it, never leave the phone.
- Gravatar is asked for a person’s picture by a one-way hash of the address, and GitHub for updates.
- No ads, no analytics, no tracking. Nothing else is contacted.
How it is protected
Checked at every step, and readable in the source.
- Browser sign-in for Fastmail and Opensolr: your passwords and two-factor codes stay in the browser.
- Encrypted on the phone with a key held by Android’s secure key store, and never in phone backups.
- Encrypted push. Fastmail encrypts every push with a key that never leaves your phone; the relay that wakes the phone passes it on without being able to read it.
- HTTPS only, for every connection the app makes.
A Fastmail account. That is all it needs.
Opensolr is optional. If you add it, the free Opensolr account runs AI search, search by meaning included, with no card and no expiry; a paid plan buys more room and more AI requests a month. The app shows your real numbers in Settings.
Disk space and bandwidth
How much mail the index holds and how much searching it serves in a month. At either limit Opensolr closes the index: indexing stops and search falls back to Fastmail's search by words until you upgrade or, for bandwidth, the month resets.
AI requests per month
Used for meaning, for the AI answer and for reading attachments. When they run out, search goes on by words only until the month resets; new mail gets its meaning later.
Without an Opensolr account
Everything works: inbox, notifications, search, contacts, notes and calendars. Search is Fastmail’s, by words, and new mail is checked every 15 minutes instead of arriving at once.
Every line is on GitHub.
Opensolr Mail is MIT licensed. Read how it signs in, how it syncs and exactly what it sends where, build the APK yourself, or fork it and make it yours.
Source code
Kotlin and Jetpack Compose. github.com/phpcip/opensolr-mail
Documentation
Installing, signing in, the inbox, notifications, search, the chat with your mail, notes and calendars, your Opensolr account, privacy. Read the documentation
Releases
Every version with its signed APK and release notes. All releases
Four steps, about a minute.
- Download the APK on your phoneopensolr-mail.apk, the latest signed release from GitHub, or install it from Google Play.
- Allow the installAndroid asks once whether your browser may install apps. Allow it for this install. From Google Play there is nothing to allow.
- Open Opensolr Mail and sign in to FastmailAdd your other Fastmail accounts in Settings.
- Optional: connect Opensolr for AI searchNow, later or never; the app works fully without it. No account yet? Create one, free.
All your Fastmail. One inbox. Found in a second.
Free, open source, every account in one place, and a search that understands what you mean and reads inside your attachments. On a free Opensolr account that never expires — need more? See the plans.