An email signature is read with every message, by every client, supplier or candidate. It is often the first piece of your brand they see, and the most repeated one. Yet in many organizations it piles up small mistakes that make it hard to read, inconsistent or simply wrong. Here are the seven most common ones in Microsoft 365 and Outlook, and how to fix each.
1. Why does my signature logo arrive as an attachment?
Because it was pasted into the signature instead of hosted. A pasted image is embedded in the message; depending on the recipient's software, it then shows as an attachment (image001.png), or not at all. The recipient thinks they received a file, and the signature loses its logo.
Fix: use an image hosted on a public server, referenced by an https:// address, in PNG or JPG — never SVG, which Outlook for Windows does not display. The guide Outlook signature logo not showing covers each case.
2. A different signature for each employee
When everyone builds their own signature, you quickly get as many versions as employees: different fonts, old logos, job titles written three ways, slogans dropped two years ago. To the recipient, it looks like a careless organization.
Fix: define one template, then apply it to everyone centrally, with variants per department or Microsoft 365 group where needed. See Microsoft 365 group signatures and our email signature templates.
3. Outdated contact details
An employee changes role, number or office, and their signature keeps announcing the old title for months. It is not just about image: a client who calls an outdated number or writes to a department that no longer exists wastes time, and so do you.
Fix: fill the signature from the directory. Name, title, department and phone then come from Microsoft Entra ID through Microsoft Graph: one update in the directory fixes the signature everywhere. See dynamic signatures with Microsoft Graph.
4. A signature made of a single image
Some organizations turn the whole signature into one image to be sure of how it looks. The result is often worse: several email programs block external images until the recipient allows them, and the signature becomes an empty frame. The phone number cannot be copied or tapped on a phone, and screen readers cannot read the text.
Fix: keep the name, title and contact details as text, with tel: and mailto: links. Keep images for the logo and, if needed, a banner, with alternative text (alt) that describes the image.
5. Too many elements
An inspirational quote, four certification logos, eight social icons, two banners and a link to the latest press release: an overloaded signature is hard to read, renders poorly on mobile and weighs down every reply in a long thread.
Fix: stick to the essentials — name, title, organization, one or two ways to reach you, the website — then add a single call to action, for example a targeted banner that changes with the current campaign. The article the email signature as a marketing channel shows how to make it work without overloading it.
6. A signature missing on mobile
A signature created in Outlook for Windows does not always follow the user: Outlook on iPhone and Android has its own signature setting, often left at "Get Outlook for iOS". Emails sent on the go therefore leave without a signature, or with the wrong one.
Fix: use a method that covers every device, such as an event-based Outlook add-in deployed by the administrator. See Outlook signatures on Mac and mobile.
7. An endless confidentiality notice
Long legal notices at the bottom of emails ("This message is confidential…") are rarely read and their legal weight is limited. Added to every reply, they lengthen threads and bury the useful contact details.
Fix: if your industry requires one, keep the notice short and target it, for example to external emails only. See the email confidentiality disclaimer and one internal and one external signature.
Quick checklist
- The logo is hosted (
https://address), in PNG or JPG, and does not show as an attachment. - Every employee uses the same template, applied centrally.
- Title, department and phone come from the Microsoft 365 directory.
- Contact details are text, with clickable links.
- The signature has a single call to action.
- The signature also appears in Outlook for iPhone, Android and Mac.
- The confidentiality notice, if any, is short.
Related reading: the free email signature checker.
Frequently asked questions
What is the most common email signature mistake?
A logo pasted into the signature instead of hosted. It is then embedded in the message and shows for many recipients as an attachment, or not at all. A hosted image, referenced by an https address, in PNG or JPG, solves the problem.
Should the whole signature be an image?
No. Several email programs block images until the recipient allows them, and an all-image signature becomes an empty frame. Name, title and contact details should stay as text; images are limited to the logo and an optional banner.
How do you keep signatures up to date when an employee changes role?
By filling the signature from the Microsoft 365 directory. Title, department and phone are read from Microsoft Entra ID through Microsoft Graph: a change in the directory updates the signature without the employee doing anything.
Why doesn't my signature appear in Outlook mobile?
Because Outlook for iPhone and Android has its own signature setting, separate from Outlook for Windows. For the same signature everywhere, you need a central method that also covers mobile, such as an event-based Outlook add-in deployed by the administrator.
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