Best Email Signature Software for Microsoft 365 (2026): 7 Tools Compared

For most Microsoft 365 teams, the best email signature software is the one that deploys to every mailbox without touching each person’s Outlook, keeps signatures consistent on desktop, web, and mobile, and doesn’t force you into an enterprise contract to get started. For small and mid-sized teams that usually means Firma; for large IT organizations that need server-side stamping on unmanaged devices it often means Exclaimer or CodeTwo; and for Microsoft-native, campaign-heavy marketing teams, Letsignit.

Below is an honest, side-by-side look at seven tools: what each is genuinely good at, who it’s for, and where it falls short.

Full transparency: I’m the founder of Firma, one of the tools on this list. I’ve kept this comparison fair and useful rather than a sales pitch. I’ll tell you exactly where Firma fits and where a competitor is the better call for Microsoft 365.

Quick comparison

Tool	Best for	Free plan	Deployment model
Firma	Small to mid Microsoft 365 teams wanting self-serve setup	Yes (up to 2 users)	Outlook add-in (also Google Workspace)
Exclaimer	Mid-market and enterprise IT teams	Free trial	Server-side stamping + add-in
CodeTwo	Microsoft 365 and Exchange environments	Free trial	Server-side (Azure) + Outlook add-in
Letsignit	Microsoft-native marketing teams	Free trial	Outlook add-in, deployed from Microsoft 365
Rocketseed	Enterprises running signature marketing	Free trial	Server-side gateway
Opensense	Sales and marketing teams with a CRM stack	Demo only	Server-side, CRM-integrated
WiseStamp	Individuals and small teams focused on design	14-day trial + free generator	Client-side, cross-platform

What actually matters for Microsoft 365

Before the tool-by-tool breakdown, the criteria that separate a good fit from a frustrating one for an M365 team:

• Central deployment, not per-person setup. The whole point is that an admin designs a signature once and it reaches every mailbox. On Microsoft 365 that usually means an Outlook add-in deployed from the admin center or server-side stamping in the mail flow. If employees still have to paste anything, you don’t have management, you have a template gallery.
• Client-side add-in vs. server-side stamping. An Outlook add-in inserts the signature as the person composes, so they see it before they send, and it works without routing your mail anywhere. Server-side stamping (Exclaimer, CodeTwo, Rocketseed) adds the signature in transit, which guarantees it appears even on unmanaged phones and third-party clients, at the cost of routing outbound mail through the vendor’s infrastructure. Neither is strictly better; it depends on whether un-removable signatures on every device is a hard requirement.
• New Outlook and mobile. Microsoft is moving everyone to the new Outlook, and the classic desktop signature stored on a device does not carry over cleanly. Tools that deploy through the add-in model or mail flow stay consistent across new Outlook, Outlook on the web, and mobile. (More on this in new Outlook vs. classic Outlook signatures.)
• Pricing model. Watch for seat minimums, “contact sales” walls, and free trials dressed up as free plans. Transparent per-seat pricing with no minimum is friendlier to a team that just wants to get started.

For the deeper version of this, see the guide to Microsoft 365 email signatures and email signature management.

The 7 tools

1. Firma

Best for: small and mid-sized Microsoft 365 teams that want to be live in minutes without a sales call.

Firma manages signatures centrally across both platforms. On Microsoft 365 you deploy the Firma Outlook add-in from your admin center, scoped to the users or groups you choose, and it inserts each person’s signature as they compose in new Outlook, Outlook on the web, and mobile. You design the signature once in the editor, and changing a detail or swapping a banner updates everyone at once. It also runs signature marketing campaigns and supports Google Workspace from the same dashboard.

• Strengths: genuinely free for up to 2 users (not a trial), transparent per-seat pricing from $1.20/seat/month billed annually ($1.50 monthly) with no seat minimum, self-serve setup, per-department and per-group templates, consistent across new Outlook and mobile.
• Considerations: Firma is newer and smaller than the incumbents, and the Microsoft 365 integration is more recent than the Google Workspace side. It uses the Outlook add-in model rather than server-side mail-flow stamping, so if you need signatures that cannot be removed on fully unmanaged devices, look at Exclaimer or CodeTwo.

2. Exclaimer

Best for: mid-market and enterprise IT teams that want server-side stamping and a mature feature set.

Exclaimer is one of the best-known signature platforms and is Microsoft 365-first. It can stamp signatures server-side in the Microsoft 365 mail flow, so a signature appears on every message from every device, and it also offers an Outlook add-in for a live preview while composing.

• Strengths: server-side stamping that works on unmanaged devices, deep template controls, analytics, and campaign features aimed at larger organizations.
• Considerations: per-user pricing across several tiers, a seat minimum on the entry plan, and an enterprise “contact sales” tier. It’s more tool than a small team needs, and setup leans on IT. (See the Exclaimer alternative page for a direct comparison.)

3. CodeTwo

Best for: Microsoft 365 and Exchange environments that want server-side signatures from a well-regarded vendor.

CodeTwo Email Signatures 365 applies signatures server-side through Azure and also offers an Outlook add-in for composing. It’s a strong, security-conscious choice for organizations already standardized on Microsoft, and it licenses per user or shared mailbox.

• Strengths: reliable server-side stamping, good support, Microsoft-certified, works well in Exchange-heavy setups.
• Considerations: per-mailbox licensing, a free trial rather than a free plan, and an admin-first experience that is more than a small team usually wants. (See the CodeTwo alternative page.)

4. Letsignit

Best for: Microsoft-native marketing teams that want signatures and campaigns deployed the Microsoft way.

Letsignit is built around the Microsoft 365 ecosystem, deployed as an Outlook add-in from the admin center, with signature management and marketing campaign features. It’s a natural fit if your organization is all-in on Microsoft and marketing wants control over signature banners.

• Strengths: Microsoft-native deployment, campaign and banner scheduling, per-group targeting.
• Considerations: per-user pricing with a free trial rather than a free plan, and it is Microsoft-focused, so it’s a weaker choice if you also run Google Workspace.

5. Rocketseed

Best for: enterprises that treat the email signature as a marketing channel.

Rocketseed runs signatures and interactive banners server-side through a mail gateway, with click tracking and campaign reporting. It is aimed at organizations that want measurable signature marketing at scale.

• Strengths: server-side consistency, strong banner and campaign analytics, enterprise support.
• Considerations: gateway-based setup and enterprise sales motion, pricing on request, heavier than a small team needs.

6. Opensense

Best for: sales and marketing teams that want signatures wired into their CRM and ABM stack.

Opensense focuses on signature-as-a-channel for revenue teams, with integrations into tools like Salesforce, Marketo, and HubSpot, and server-side deployment across Microsoft 365 and Google.

• Strengths: deep marketing and CRM integrations, targeting by audience, analytics for pipeline attribution.
• Considerations: built for larger go-to-market teams, demo-and-quote sales process, more platform than a team that just needs tidy signatures.

7. WiseStamp

Best for: individuals and small teams whose priority is a beautifully designed personal signature.

WiseStamp is popular, design-forward, and cross-platform, with a free standalone generator and paid plans for individuals and teams. It works with Outlook but installs client-side per user rather than deploying server-side across a Microsoft 365 domain.

• Strengths: polished templates, social icons, easy for one person, free generator.
• Considerations: more individual-focused; centralized fleet management across an M365 tenant is not its core strength. (See the WiseStamp alternative page.)

So which should you choose?

• Small or mid-sized M365 team, want to start today without a sales call: Firma. Free for up to 2 users, transparent per-seat pricing, add-in deployed from your admin center in minutes.
• Enterprise IT that needs un-removable signatures on every device: Exclaimer or CodeTwo for server-side stamping.
• All-in on Microsoft, marketing wants banner control: Letsignit.
• Signature as a measurable marketing channel at scale: Rocketseed or Opensense.
• One person who wants a gorgeous signature: WiseStamp.

There is no single “best” tool, only the best fit for your size, platform mix, and whether server-side stamping is a hard requirement. If you’re a growing team on Microsoft 365 (and maybe Google Workspace too) that wants central control without an enterprise contract, try Firma free.

Frequently asked questions

Does Microsoft 365 have built-in email signature management? Only partially. You can add a disclaimer to all outbound mail with an Exchange transport rule, but it is appended server-side after sending, is not personalized per user in the compose window, and does not show while people write. A personalized, on-brand signature that each person sees as they compose needs an Outlook add-in or a dedicated signature tool.

What is the difference between an Outlook add-in and server-side stamping? An add-in inserts the signature as the person composes, so they preview it before sending, and no mail is routed through a third party. Server-side stamping adds the signature in transit, which guarantees it on every device including unmanaged phones, but routes outbound mail through the vendor’s infrastructure. Firma and Letsignit use the add-in model; Exclaimer, CodeTwo, and Rocketseed can stamp server-side.

Will managed signatures work in the new Outlook? Yes, when the tool deploys through the add-in model or the mail flow. A signature stored only on a classic Outlook desktop install does not migrate cleanly to new Outlook, which is one reason centrally managed signatures are more reliable. See new Outlook vs. classic Outlook signatures.

Is there free email signature software for Microsoft 365? Most tools offer a free trial rather than a free plan. Firma is free for up to 2 users on an ongoing basis, which covers very small teams; beyond that, pricing is per seat from $1.20/user/month billed annually.

Can one tool manage both Microsoft 365 and Google Workspace? Yes. Firma manages both from one dashboard: the Outlook add-in on Microsoft 365 and a 1-click Marketplace install on Google Workspace. Exclaimer and Opensense also support both platforms; CodeTwo and Letsignit are Microsoft-focused.