Product images: Microsoft, Grammarly and SaneBox official pages
I have worked in IT for about twenty years, and the Outlook question I hear most is not "which AI is smartest" but "which one will not get me in trouble with my admin". Outlook is where contracts, invoices and customer complaints live, so an AI email assistant has to earn access to it. This guide follows the searches people run next on Google (free, 365, app, download, how to use it) and checks each answer against the vendors' own pages, all read on October 28, 2026.
Quick answer- Best if you already pay for Microsoft 365: Copilot in Outlook, which Microsoft says drafts emails, summarizes threads, coaches tone and prioritizes your inbox.
- Best free way to improve what you write: Grammarly, whose Free account works in Outlook through its desktop app.
- Best for taming a crowded inbox rather than writing: SaneBox, which sorts unimportant mail and works with any email client.
- Best for sales emails: Lavender, with a free Basic plan limited to 5 analyzed emails a month.
Jump to: Three jobs | Outlook 365 and Copilot | How to use AI in Outlook | Free options | App | Download | Grammarly, SaneBox, Lavender | Limits | Privacy | Compare | Final pick | FAQ
This is general information. Features and plans change often, and your organization may limit what you can turn on.
Best AI Email Assistant for Outlook Depends on Which Job You Need Done
People searching for an AI email assistant want three different things, and the tools do not overlap as much as the marketing suggests. A writer drafts or rewrites messages. A coach checks tone and clarity before you send. A sorter decides which messages deserve your attention at all.
Pick the job first. If your problem is two hundred unread messages, a better writer will not help. If your problem is one hard email to a client, a sorter will not help either.
My take (20 years in IT): Before you install anything, spend one morning counting. How many messages did you read and ignore, and how many did you struggle to write? Whichever number is bigger tells you whether to look at a sorter or a writer. Most people guess wrong, and they buy a writing tool for an attention problem.
AI Email Assistant for Outlook 365: What Copilot in Outlook Does
Image: Microsoft (official support page)
For Microsoft 365 users, the first stop is Copilot, which Microsoft describes on its Welcome to Copilot in Outlook page as AI-powered help to write emails quickly, turn long threads into short summaries and create a meeting invitation from within an email thread. Microsoft's FAQ for Copilot in Outlook (last updated August 2026) lists the full set of features, and these are the ones that matter for email.
- Draft with Copilot. Generates a full draft from a prompt, based on thread context and organizational information.
- Summary by Copilot. Pulls key points out of an email thread, with numbered citations back to the messages.
- Coaching by Copilot. Suggests changes to tone, sentiment and clarity on your own draft.
- Prioritize my inbox. Marks incoming mail as high, low or normal priority and gives a reason.
- Email triage and rules in chat. Pin, flag, archive or delete messages, and create or manage Outlook rules in plain language.
- Schedule with Copilot. Builds a meeting invitation from a thread, with a title, agenda and the people on the thread.
Image: Microsoft (official support page)
Access depends on your plan. Microsoft's Where can I get Microsoft Copilot? page (last updated August 2026) says Microsoft 365 Personal and Family subscriptions include Copilot in apps such as Word, Excel, PowerPoint, Outlook and OneNote, with AI credits. For work, it says you need an active Business or Enterprise Microsoft 365 subscription before you can subscribe to Microsoft Copilot.
Image: Microsoft (official pricing page)
On its Copilot business pricing page on October 28, 2026, Microsoft listed Microsoft 365 Business Premium with Copilot at $32.00 per user per month and Business Standard with Copilot at $23.50, both paid yearly. The Copilot Business add-on was listed at $18.00, marked down from $21.00, per user per month paid yearly. These are Microsoft's list prices and can change, and the add-on needs a base Microsoft 365 plan.
The same page says Copilot Chat is included at no additional cost with eligible Microsoft 365 plans and includes Copilot in Outlook. The support FAQ, on the other hand, says Chat with Copilot inside Outlook is available only to businesses with a Microsoft Copilot subscription. Both statements are Microsoft's, and they describe different features, so ask your admin what your account actually shows.
How to Use AI in Outlook Email: Draft, Summarize, Coach and Prioritize
Draft a new message
Image: Microsoft (official support page)
In new Outlook, Microsoft says to select Home, then New mail, choose the Copilot icon on the toolbar and pick Draft (classic Outlook calls it Draft with Copilot). Type a prompt, select Generate, then use options such as Make it shorter, Make it longer or Change Tone. If the result is wrong, you can Retry, and when you are happy you select Keep it, edit the text and select Send yourself. Microsoft's drafting page adds that you can also select text inside an email and ask Copilot to change just that part.
Image: Microsoft (official support page)
One detail trips people up. Microsoft notes that in new Outlook and Outlook on the web, Draft with Copilot does not support messages written in plain text. To switch, go to Settings, then Mail, then Compose and reply, and choose HTML.
Summarize a long thread
Image: Microsoft (official support page)
Open the conversation and select Summary by Copilot (classic Outlook may say Summarize) at the top. Microsoft says Copilot scans the thread for key points and shows a summary at the top, sometimes with numbered citations that take you to the matching email. In new Outlook, attachments in PDF, PowerPoint or Word format can be summarized with Summarize a file, according to Microsoft's summarize page.
Image: Microsoft (official support page)
My take (20 years in IT): Use the citations. A summary that cites its sources lets you open the one message that matters, and that is the habit that stops summaries from becoming a guess. If a thread involves money, dates or a commitment, read the original message before you reply to a summary.
Coach your own draft
Image: Microsoft (official support page)
Write your message, select the Copilot icon and choose Coaching by Copilot. Per Microsoft's coaching page, Copilot reviews the email and suggests changes to tone, clarity and reader sentiment. You can accept them one at a time or select Apply all suggestions, which regenerates the text with every improvement.
Let Copilot prioritize your inbox
Image: Microsoft (official support page)
Prioritize my inbox is the sorter among Copilot's features. Microsoft says Copilot reviews emails as they arrive, assigns high, low or normal priority based on factors such as the people on the thread, their job titles and the content, and shows a short reason. It says mail is not delayed, because this happens alongside delivery.
Image: Microsoft (official support page)
To start, Microsoft says to open the arrow next to the Copilot button, choose Prioritize and give at least one high priority instruction, for example "It's from my manager". High priority mail gets an up arrow in the message list. The low priority marker is off by default and can be turned on in Settings under Copilot and Prioritize. Microsoft also says Copilot prioritizes only mail received after you turn the feature on, and that it does not evaluate mail in folders other than your Inbox, mail you send to yourself, out-of-office replies or meeting invitations.
Image: Microsoft (official support page)
Draft inside Chat
Image: Microsoft (official support page)
The drafting page also describes a second route. Start a new email, reply or forward, select Help me write or Help me reply, and Chat opens beside your message. The FAQ says Chat with Copilot in Outlook works with a work or school account in new Outlook for Windows or Outlook on the web.
Image: Microsoft (official support page)
AI Email Assistant for Outlook Free, and the Best Free Options
"Free" can mean three different things here: a plan that never expires, a trial, or a feature included in something you already pay for. Counting them separately avoids surprises.
| Tool | What is free | Limit as listed |
|---|
| Grammarly | Free account works in Outlook through the desktop app | 100 AI prompts a month on Free, per its plans page |
| Lavender | Basic plan, free forever, Gmail and Outlook 365 | Analyze 5 emails and personalize 5 emails a month |
| SaneBox | 7 day free trial, no credit card required | Trial only, not a free plan |
| Copilot in Outlook | Microsoft says Copilot Chat is included with eligible Microsoft 365 plans | Which features you get depends on your plan and admin |
For AI for email management without paying, the realistic free stack is your existing Outlook rules and filters plus Grammarly Free for writing.
AI Email Assistant for Outlook App: New Outlook, Mobile and Desktop
Where you use Outlook changes which AI features show up. Microsoft's FAQ says Chat with Copilot works only in new Outlook for Windows and Outlook on the web with a work or school account. Its Prioritize page says that when you turn the feature on in one place, such as your desktop, it works on all clients, including mobile. Language detection for summaries is described as available on Android, iOS and Mac now, and coming to Windows and web.
Image: Microsoft (official support page)
Third-party tools work differently. Grammarly says that once you install it on your desktop, on Windows or Mac, its suggestions appear as you type in Outlook. SaneBox says it works wherever you check your email and needs nothing to download, because it sorts mail at the account level. Lavender says its Email Coach works in Gmail and Outlook 365 after you install it.
AI Email Assistant for Outlook Download: What You Actually Have to Install
| Tool | Download needed? | How it connects |
|---|
| Copilot in Outlook | No separate download | Built into Outlook, turned on by plan and admin settings |
| Grammarly | Yes, Grammarly for Windows or Mac | Desktop app adds suggestions in Outlook and other apps |
| Lavender | Install the Email Coach | Works with Gmail and Outlook 365, per its page |
| SaneBox | No | Connects to your email account and sorts mail |
Copilot is not a download you can add on your own. Microsoft's pages tell you to select the Copilot icon in Outlook, and "If you're unable to access Copilot in Outlook, check with your IT admin." For anything else, download only from the vendor's own link on the pages cited here, and ask IT before you grant a new app access to a work mailbox.
Grammarly, SaneBox and Lavender, and Who Each One Fits
Image: Grammarly (official page)
Grammarly, for better writing everywhere
Grammarly for Microsoft Outlook is a writing assistant first. The page says it catches typos, punctuation and commonly confused words, rewrites for tone, length and formality, and can generate text from a prompt. A Free account works in Outlook, and Pro adds fluency suggestions and more.
Image: Grammarly (official page)
Image: Grammarly (official page)
On its plans page, Grammarly lists Free at $0 with 100 AI prompts a month and Pro at $12 USD (check the billing period on the page) with 2,000 AI prompts per member a month, plus rewriting full sentences, tone changes and plagiarism and AI text detection. Grammarly also says you may opt out of letting it use your content to improve its products or train its models, and that it does not train on content from certain business users or users whose accounts originate in the EU or UK.
Skip it if your main problem is volume. Grammarly will polish an email, but it does not decide which emails you should open.
Image: SaneBox (official page)
SaneBox, for a quieter inbox
SaneBox is a sorter. It says it automatically filters out unimportant emails, unsubscribes you from unwanted senders in one click and reminds you to follow up when someone does not reply. Its feature list includes a Daily Digest of unimportant messages you have not opened, Snooze, and BlackHole for senders you never want to see again.
Image: SaneBox (official page)
Image: SaneBox (official page)
The pricing page lists three plans with a 7 day free trial. Snack is $4.54 a month billed every 2 years for 1 email account and 2 features, Lunch is $7.46 for 2 accounts and 6 features, and Dinner is $22.04 for 4 accounts and all features. Those prices assume billing every 2 years, and the page also offers annual and monthly options, so compare the same billing period before you decide. SaneBox says it looks at the basics such as sender, subject line and date, and that it never stores full emails or attachments. That is the vendor's statement.
Skip it if you need help writing. SaneBox does not draft messages.
Image: Lavender (official page)
Lavender, for emails that need a reply
Lavender is a coach built mainly for sales. Its page says the Email Coach works in Gmail and Outlook 365, and lists a free Basic plan that analyzes 5 emails a month and personalizes 5 a month. Paid plans on the page include Starter at $27 a month for individuals, billed annually, Individual Pro at $45 and a Team plan at $89 per seat, billed annually, with a 7 day trial that includes all integrations. Lavender says it is SOC2 certified and GDPR compliant, which is its claim. For a full sales-email comparison, see Best AI Email Assistant for Sales in 2026.
Skip it if you rarely send cold or sales email. The free tier will run out quickly if you send more than a few a week.
What Copilot in Outlook Cannot Do
Image: Microsoft (official support page)
The limits are worth knowing before you roll it out. Microsoft's FAQ says Copilot scenarios are available on a user's primary mailbox, archive mailbox, and shared and delegate mailboxes they can access, but not on group mailboxes or on mailboxes that are not hosted on Exchange Online. It cannot access S/MIME or Double Key Encryption encrypted emails. Prioritize currently supports Tier 1 languages only. And Microsoft repeats a warning on its Welcome page: because Copilot uses GPT, "it may create things you didn't expect", so review and verify what it produces.
My take (20 years in IT): Set a rule for every AI-written email: you read it as if a stranger wrote it. Check names, dates, amounts and any promise. A thirty second review costs less than one retraction email, and it is the control that no setting replaces.
Privacy and Safety Before You Connect Your Mailbox
An email assistant sees your email by design, so read the privacy terms before you turn it on. For Copilot, Microsoft's FAQ points business users to its data, privacy and security page for Microsoft Copilot, and home users to a separate page for Copilot in Microsoft 365 apps for home. On its pricing page, Microsoft says that with enterprise data protection, prompts and responses stay within the Microsoft 365 service boundary and are not used to train the underlying large language models. That is Microsoft's statement for the plans it covers.
For third-party tools, the claims above (Grammarly's opt-out controls, SaneBox's statement that it does not store full emails, Lavender's SOC2 and GDPR claims) are what each company says about itself. Neither I nor this guide has audited them. If you handle client, legal, medical or financial mail, get your IT or compliance team to approve the tool first.
AI Email Assistants for Outlook Compared
| Tool | Best for | Price as listed | Link |
|---|
| Copilot in Outlook | Drafting, summaries, coaching and prioritizing inside Outlook | Business add-on $18.00 (from $21.00) per user per month, paid yearly | Visit site |
| Grammarly | Writing and tone in every app | Free, Pro $12 USD (check billing period) | Visit site |
| SaneBox | Sorting and reducing inbox clutter | Snack $4.54 a month billed every 2 years, 7 day trial | Visit site |
| Lavender | Sales email coaching | Free Basic, Starter $27 a month billed annually | Visit site |
Prices are the ones the vendors listed on October 28, 2026 and they change. Copilot's price depends on the base Microsoft 365 plan, and Microsoft's own pages say usage-based features are billed separately.
Final Recommendation
If your organization already pays for Microsoft 365 and has turned Copilot on, start with Copilot in Outlook. Try Summary by Copilot and Coaching by Copilot first, because they save time without writing anything on your behalf. If you cannot get Copilot, Grammarly Free is the simplest way to improve your writing in Outlook today. Choose SaneBox when the problem is a crowded inbox, and consider Lavender only if sales email is your daily work. Whichever you choose, ask IT before connecting a work mailbox.
FAQ
Is there a free AI email assistant for Outlook?
Yes, in the sense of a free starting point, not a free copy of Copilot. Grammarly says a Free account works in Outlook for corrections, rewrites and its generative AI, and its plans page lists 100 AI prompts a month on Free. Lavender lists a free Basic plan that analyzes 5 emails and personalizes 5 emails a month in Gmail and Outlook 365. SaneBox offers a 7 day free trial rather than a free plan.
Does Outlook have AI built in?
Microsoft has Copilot in Outlook, which its support pages describe as drafting emails, summarizing threads, coaching tone and clarity, prioritizing the inbox and creating meeting invitations. Which features you see depends on the account and plan, so check with your IT admin or the Microsoft pages linked in this guide.
Do I need Microsoft 365 Copilot to use AI in Outlook?
Not for every feature. Microsoft says Copilot Chat is included at no additional cost with eligible Microsoft 365 plans and also includes Copilot in Outlook, and its Microsoft 365 Personal and Family plans include Copilot features in Outlook. Other features, such as chatting with Copilot inside Outlook, are described as available to businesses with a Microsoft Copilot subscription. The exact mix changes, so read the current plan page.
Can Copilot read encrypted or signed emails?
Microsoft says Copilot in Outlook cannot access S/MIME or Double Key Encryption encrypted emails, and that its email features are not supported on signed or encrypted emails, on emails with IRM, or on some MIP labeled emails.
Is it safe to use Grammarly, Lavender or SaneBox with work email?
Each vendor publishes its own privacy claims, which are summarized above, but those are claims, not audits you have read. Ask your IT team before connecting a work mailbox, and for regulated or confidential mail, use only tools your organization has approved.
How do I turn on Prioritize in Outlook?
Microsoft says that on Windows you select the arrow next to the Copilot button at the top right of the window and choose Prioritize, then give Copilot at least one high priority instruction. On Mac you use the What's New pane and select Try it. Microsoft notes the feature is being rolled out gradually, so it may not be visible yet.
Try These Tools
Links go to each vendor's official page.
Sources
All pages were checked on October 28, 2026 in their English versions.
- Microsoft Support, Welcome to Copilot in Outlook (September 23, 2026)
- Microsoft Support, Draft an email message with Copilot in Outlook
- Microsoft Support, Get email coaching with Copilot in Outlook
- Microsoft Support, Summarize an email thread with Copilot in Outlook
- Microsoft Support, Prioritize my inbox
- Microsoft Support, Frequently asked questions about Copilot in Outlook (August 2026)
- Microsoft Support, Where can I get Microsoft Copilot? (August 2026)
- Microsoft, Copilot business plans and pricing
- Grammarly for Microsoft Outlook
- Grammarly, Prices and Plans
- SaneBox, Home and Pricing
- Lavender, Email Coach overview and pricing
This guide is general information. Plan limits and prices change often, so check the vendor's page before you decide.
Last updated: October 28, 2026.
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