For most companies on Microsoft 365 the common choices are Exclaimer and CodeTwo. If you also run Google Workspace, pick a tool that covers both (Exclaimer, Rocketseed, WiseStamp or SignetMail). If data must stay on your own server, or you want a free option for up to 50 users, SignetMail is the only one on this list that does that.
Disclosure: this list is written by SignetMail, which is also on it. Prices come from public price lists and comparison pages (G2, WiseStamp) in November 2026, in US dollars per user per month. Vendors change them often, so check before you buy.
How to choose a signature tool
Before comparing prices, answer four questions:
- Which platforms do you run? Only Microsoft 365, or Google Workspace too, for example in a subsidiary?
- How should the signature reach the message? A tool can add it on the server as mail leaves the company (works from every device, but the sender doesn't see it while writing), or with an Outlook add-in while composing (visible, but limited to supported clients).
- Where does the data live? Most tools are a vendor cloud service. If you have strict data rules, check where it runs and whether it can run on your side.
- How many users? Pricing is per user, often with a minimum number of licenses.
Comparison at a glance
| Tool | Platforms | How it adds the signature | Trial | From |
|---|---|---|---|---|
| Exclaimer | Microsoft 365, Google Workspace, Exchange | In the vendor cloud or with an Outlook add-in | 14 days | about $0.90, minimum 10 users |
| CodeTwo | Microsoft 365 | On the server (Exchange Online) or with an Outlook add-in | 14 days | about $1.22 billed yearly |
| Signature 365 | Microsoft 365 | Outlook add-in, optional mail routing | 14 days | on their site |
| Letsignit | Microsoft 365, Google Workspace with fewer features | Mainly an Outlook add-in | yes | about $2 |
| WiseStamp | Microsoft 365, Google Workspace | No mail flow changes | 14 days | $19 a month plus $1 per employee |
| Rocketseed | Microsoft 365, Google Workspace, Exchange | On the server, as a managed service | 14 days, 50+ employees | about $1.25 |
| SignetMail | Microsoft 365, Google Workspace | Outlook add-in, agent for classic Outlook, Gmail API | free for up to 50 users | free during the public beta |
1. Exclaimer
The most widely used tool in this category. It supports Microsoft 365, Google Workspace and on-premises Exchange, and adds the signature in the cloud or with an Outlook add-in. Higher tiers add analytics, A/B testing and CRM integrations. A fit for mid-size and large companies that want a service run entirely by the vendor.
2. CodeTwo Email Signatures 365
A Polish vendor focused on Microsoft 365. It can add the signature on the server as mail passes through Exchange Online, so it is the same from every device, or with an Outlook add-in. Google Workspace is not supported. A good choice if you run only Microsoft 365 and want a proven product.
3. Signature 365
A Microsoft 365 service from Symprex, with an Outlook add-in and optional routing of mail through their service. It holds ISO 27001 and SOC 2 certifications and offers phone support. More in A Signature 365 alternative.
4. Letsignit
A French vendor with a good template editor and signature campaigns. It adds the signature mainly through an Outlook add-in, so mail flow stays unchanged. Google Workspace is supported, with fewer features.
5. WiseStamp
Started as a tool for individuals and now has company plans for Google Workspace and Microsoft 365. Pricing is a monthly base plus an amount per employee. A fit for smaller teams that want to start quickly.
6. Rocketseed
A managed service that always adds the signature on the server. It supports Microsoft 365, Google Workspace, Exchange and hybrid setups. The trial is only for companies with 50 or more employees.
7. SignetMail
A product from Slovenia that you install on your own server (Docker or a Windows installer) or use in the EU cloud. It takes data from Entra ID or Google Workspace and adds the signature with an Outlook add-in (phones included), an agent for classic Outlook on Windows, and the Gmail API. Mail flow stays unchanged. It is free for up to 50 active users. It is a younger product without certifications such as ISO 27001 or SOC 2.
Which tool fits you?
- Microsoft 365 only, mid-size or large company: CodeTwo or Exclaimer.
- Microsoft 365 and Google Workspace: Exclaimer, Rocketseed or SignetMail.
- Data must stay with you: SignetMail on your own server.
- Up to 50 users and no budget: SignetMail. For a single person, the free signature generator is enough.
- Certifications are a vendor requirement: Exclaimer, CodeTwo or Signature 365.
Frequently asked questions
Can Microsoft 365 apply a consistent signature without an extra tool?
Partly. An admin can set up an Exchange Online rule that appends text to every outgoing message. That text is the same for everyone, the sender doesn't see it while writing, and in replies it lands below the quoted text. For each employee's own details you need a tool.
Which is better: a server-side signature or one in Outlook?
A server-side signature works from every device, but the sender doesn't see it and mail flow has to change. An Outlook add-in signature is visible while writing and leaves mail flow alone, but works only in supported clients: Outlook for Windows, Mac, the web, iOS and Android.
Is there a free signature tool for Microsoft 365?
Most vendors offer only a 7 to 14-day trial. SignetMail is free for up to 50 active users, with every feature during the public beta.
Try SignetMail for free
Free during the public beta, with every feature and no card. We help pilot companies with the setup.