Key Takeaways
- Gmail gives you 10,000 characters and counts your logo against them. The limit is generous for text and tight for images, which is the first sign that a signature is a rendering problem rather than a design one (checked 2026-10-16).
- The signature you build and the signature people receive are two different objects. Mail clients re-render your footer on arrival, so the only layouts that survive are tables with inline styles and web-safe fonts.
- Every client stores signatures in its own place, and the phone is a separate setup. A Gmail mobile signature is a per-account setting that applies only to mail sent from the app, so the desktop version you spent an hour on never reaches it.
- Outlook's web signature editor has a documented hyperlink problem. Building the block in a new message and pasting it back is the workaround people land on, which also happens to be the safest way to install any signature anywhere.
- A booking link belongs in the footer, not in the body of a first email. Sitting passively below your name, it asks nothing of the reader and still gives them a one-click next step.
Gmail gives you 10,000 characters for a signature. Almost nobody runs out, and almost everybody still ends up with a footer that looks broken somewhere, because the character count was never the constraint. The constraint is that your signature gets stored by one program, transmitted as HTML, and redrawn by a different program on hardware you will never see.
So this is the install guide, not the design guide. For what goes in the block in the first place, the nine signature layouts and the four lines that carry the weight covers that side. What follows is where each client hides the setting, and which of your choices won't survive the trip.
What a signature actually is once it leaves your outbox
A mail signature is a fragment of HTML appended to your message and handed to a renderer you don't control. That renderer is allowed to ignore you.
This is why signature HTML looks like it was written in 2004. The layout has to be a table, because mail clients support modern CSS layout inconsistently. Styles have to be inline on each element, because many clients strip anything in a <style> block. Fonts have to be web-safe, because the recipient's machine only has the fonts it has.
The practical version of that rule set is short:
- Tables for layout. One row, one or two cells. Not flexbox, not grid.
- Inline styles only. Every colour, size and margin declared on the element itself.
- A web-safe font stack. Arial and Helvetica with a generic sans-serif fallback renders predictably nearly everywhere.
- Hosted images, referenced by URL. Images pasted in from your disk get stripped or converted to attachments by a meaningful share of clients.
- Text, not a picture of text. A signature exported as a single PNG is unselectable, unsearchable, invisible to screen readers, and dead if images are blocked.
That last one comes up constantly. A four-comment r/careeradvice thread on building a professional signature suggests composing it in a word processor and pasting it in, then asks whether signatures should be JPEGs. The JPEG instinct is the expensive one: it trades every accessibility and copy-paste property of real text for a layout that still breaks when images are off.
Where each mail client hides the setting
Five paths, verified on 2026-10-16. The order below is roughly by how often people get stuck.
Gmail on desktop
Click the gear icon at the top right, then See all settings. The Signature section sits in the General tab. Create or edit the block there, then scroll to the bottom and click Save Changes, which is the step people miss, because the page gives no other confirmation.
Gmail allows up to 10,000 characters and counts an image against the limit, so an error on save means a smaller image rather than shorter text. You can hold several signatures with different defaults for new mail and for replies.
New Outlook for Windows and Outlook on the web
Both use the same path now. Open Settings (the gear), then Accounts, then Signatures, then Add signature with the plus icon. Name it, build it, and save. Editing later is the pencil icon next to the signature name.
To put one into a specific message rather than relying on the default, open a new mail and use Signature in the Insert group on the Message tab.
Classic Outlook for Windows
Two paths reach the same dialog. From a new message: Message, then Signature, then Signatures. From the main window: File, then Options, then Mail, then Signatures.
Microsoft documents one caveat here worth reading before you add a logo: Vector Markup Language tags inside the signature can make elements arrive as attachments instead of inline images (checked 2026-10-16). That is the mechanism behind the paperclip icon on your empty one-line replies, and it is a property of the markup rather than something you misconfigured.
Apple Mail on Mac
Open Mail, then Settings, then Signatures. Pick the account in the left column, then click the add button below the middle column and name the new signature. Build it in the right-hand preview pane: the Edit menu turns selected text into links, the Format menu handles fonts and colour, and an image goes in by dragging it into the preview.
Two details cause support threads. If All Signatures is selected when you create one, you have to drag it onto an account before it becomes usable. And the Place signature above quoted text checkbox decides whether your footer sits above or below the original message on replies, which is why some signatures end up buried under four levels of quoting.
The Gmail app on iOS and Android
This is the one that catches people. The Gmail app keeps a separate Mobile Signature that applies only to mail sent from the app, per account.
On iOS: tap Menu, then Settings, then Signature settings under "Compose and Reply", then turn on Mobile Signature. On Android: tap Menu, scroll to Settings, choose the account, then Mobile signature. If you never set one, the app falls back to your desktop signature. Google's documentation describes the field as text and does not state whether formatting or links are supported, so treat it as plain text until you've tested it.
Skip this section if you only ever send from one machine and one client. The multi-client problem is what creates mismatched signatures, and if you don't have it, you don't need to solve it.
Apple's published iPhone Mail settings documentation doesn't spell out a signature path at all, which is worth saying plainly rather than guessing at a menu tree: if you send from Apple Mail on a phone, confirm that setting on the device itself.
Adding the booking link so it still works after the paste
A link is the highest-value element in a footer and the one most likely to arrive broken. Two problems recur.
The first is that signature editors are not full HTML editors. A twelve-comment r/Outlook thread on adding a link in new Outlook is about exactly this, from someone trying to make a banner image clickable. A separate eight-comment r/Office365 thread reports that inserting a hyperlink into the Outlook online signature editor fails outright, and the workaround offered in the thread is to compose the signature inside a new email, add the link there where the editor behaves normally, then copy the finished block into the signature field.
That workaround is worth adopting as the default method even where the editor works. Build once, paste everywhere, and the same markup lands in every client.
The second problem is link rot. A booking URL in a footer is a promise about your availability that you made once and stopped thinking about, and it outlives job changes, calendar migrations and abandoned trials. The fix is structural: point the footer at a stable personal URL whose availability is resolved at click time. meetergo's personalised booking link works that way, and the calendar link generator produces a plain one without an account.
On placement: keep it in the footer. The friction sales teams describe comes from dropping a scheduling link into a cold first email, which asks the recipient to commit before they've agreed to anything. In a signature the same link makes no demand and costs nothing to ignore. The booking-link etiquette guide covers when it earns promotion into the body.
Why it looks wrong on someone else's screen
Your signature renders correctly for you by definition, because you are looking at it in the client that created it. The failures happen elsewhere.
Dark mode inverts things you didn't plan for. A one-month-old r/ProtonMail thread asks how to make a signature PNG that flips between day and night mode, and the answer is that it mostly can't: a two-comment thread's worth of workarounds doesn't change that a flat image has one set of colours. A three-comment r/techsupport thread on dark mode altering the email body shows the same force acting on text. Clients that force dark mode recolour your content, and a dark logo on transparency becomes a dark shape on a dark field.
Quoting degrades styling. By the fifth message in a thread your footer is nested inside several levels of quote formatting, and some clients drop the styling entirely at that depth. Anything that depends on colour to be legible fails here first.
Phone screens are narrow. A two-column signature with a photo beside six contact lines reflows into a tall stack, under every message in the thread. It isn't broken, only far longer than you intended.
The testing burden is real enough that people build tools for it. An eight-comment r/InternetIsBeautiful thread announcing a generator aimed at working across all mail clients exists because hand-rolling compatible signature markup is easy to get subtly wrong.
Four mistakes that survive the install
- Saving without checking the save. Gmail's settings page needs an explicit Save Changes at the bottom, and Apple Mail wants a new signature dragged onto an account before it does anything. In both cases the signature appears to exist and isn't attached to anything.
- One signature for every context. Your reply signature should be shorter than the one on a first contact. Most clients let you set both defaults independently, and almost nobody does.
- Embedding the image instead of hosting it. Pasting a logo from your disk is how it becomes an attachment on every message you send. A publicly reachable image URL avoids most of it, and a text-only footer avoids all of it.
- Never reading it on a phone. Send yourself one message, open it on the device you'd read a client's email on, and reply once. Most signature failures surface in those three steps.
Where meetergo fits
meetergo is a European scheduling and revenue-pipeline tool used across sales, consulting, recruiting and healthcare, with a free browser-based email signature feature built around the constraints above rather than around visual templates.
The generator outputs a table layout with inline styles and an Arial and Helvetica stack, the format that survives Outlook, Gmail, Apple Mail and Thunderbird. It takes a photo or logo as a hosted URL precisely because uploaded images get stripped by many clients. Your booking link renders as a real button with your own label and accent colour, both a rich and a plain-text version go to the clipboard so the paste works into either kind of field, and an optional small-print line holds the company register details EU businesses must include. It all runs in your browser with nothing sent to a server.
The booking link it builds against is on the free plan, so a working footer link doesn't require a paid tier. Data sits in Germany under EU law with no US corporate parent, which matters if that link collects names and email addresses from people in Europe. Wider pipeline pieces like automated reminders and round-robin routing sit behind the paid tiers on the pricing page.
The honest gap: there's no admin console for pushing one branded signature across a Microsoft 365 or Google Workspace tenant. Enforcing a standard footer on 400 employees is a dedicated signature-management category, and this isn't it. For a team under twenty people who set their own signatures anyway, that costs nothing.
One naming confusion worth clearing up, since it sends people to the wrong product: a mail signature is the footer block on your messages. An electronic signature is a legally binding mark on a document. They share a word and nothing else.
Build a booking link for your signature on the free plan. No credit card required.
Booking + video conferencing in one tool.
Booking + video conferencing in one tool.
FAQs
How do I add a signature to mail on a phone?
In the Gmail app it's a separate setting from your desktop signature: Menu, then Settings, then Signature settings on iOS or Mobile signature on Android, per account. It applies only to mail sent from the app. Other mobile clients vary, and Apple's iPhone Mail documentation doesn't publish the path, so check it on the device.
Why does my logo arrive as an attachment?
Because the image is embedded in the message rather than referenced from a URL. In classic Outlook, Microsoft documents Vector Markup Language tags in the signature as a cause of elements appearing as attachments instead of inline images. Hosting the image publicly and linking to it fixes most cases; a text-only footer fixes all of them.
Can I use my brand font in a mail signature?
Only if the recipient has it installed, which you can't rely on. Declare a web-safe stack and accept that your footer is slightly off-brand, or render the wordmark as a hosted image and keep all contact details as live text.
How long should a mail signature be?
Four lines covers most professional email. European companies carrying statutory register details run six to nine, because those lines are a legal requirement rather than a design choice. If your footer is longer than the shortest message you regularly send, cut it.
Should the booking link be a button or a text link?
A button gets noticed and a text link survives more rendering conditions. An inline-block styled anchor behaves like a button in clients that support it and degrades to a styled link where they don't, which is the usual compromise.
Why does my signature look fine in Gmail and wrong in Outlook?
Different rendering engines. Outlook on Windows has historically used a word-processing engine for HTML mail rather than a browser engine, so spacing, margins and anything beyond table layout can shift. Testing into a real Outlook inbox is the only reliable check.
