Email signature generator › Blue underline

Blue underlined text you did not ask for

Your phone number arrives blue and underlined. Your address becomes a map link. You did not write those links — the recipient's client created them, and the fix is to create them first, yourself.

What is doing it

Mail clients scan message text for things that look like phone numbers, addresses, dates and email addresses, and turn them into tappable links. On mobile this is genuinely useful: a number you can call with one tap. The side effect is that the client styles those links with its own default — usually blue and underlined — which overrides your careful grey.

iOS is the most aggressive, followed by the Gmail app on Android and Outlook mobile. Desktop clients do it less, which is why the problem often appears only when someone reads your mail on a phone.

The reliable fix: get there first

Auto-detection only applies to text that is not already a link. If you wrap the phone number in a real anchor yourself, the client leaves it alone, and your styling applies:

<a href="tel:+41791234567" style="color:#444; text-decoration:none">+41 79 123 45 67</a>

You get the tappability, which you wanted, and the colour you chose. Do the same for the email address with mailto: and for any web address. This is better than fighting the detection, because it gives the reader the useful behaviour rather than removing it.

The address case

A postal address gets turned into a maps link on iOS. If you do not want that, the usual approach is to break the pattern the detector looks for — putting the postal code and city on separate lines, or using a middle dot instead of a comma between elements. It is a workaround rather than a fix, and it is worth asking whether a maps link is actually harmful before spending effort on it.

Why colour alone does not hold

Setting a colour on the containing cell does not survive, because the client-generated link carries its own inline style applied after yours. Only an anchor you wrote, with the style on the anchor itself, wins — and even then some clients override link colour in dark mode, which is a separate battle not worth fighting.

Do not remove the underline everywhere

There is a temptation to set text-decoration:none on every link in the signature. For the phone number, where the surrounding context makes it obvious, that is fine. For a web address, removing the underline and using a grey close to the body text leaves the reader no signal that it can be clicked. Keep one visual cue: either the underline or a distinctly different colour.

The email address case

An email address written as plain text is turned into a mailto: link by nearly every client, with the same blue underline. Writing the anchor yourself gives you the colour back, and it also lets you control the visible text: you can show anna@acme.com while the href carries a subject line or a different address if that is useful.

Dark mode makes this worse

Several clients override link colours in dark mode regardless of what you declared, on the theory that your colour may not have enough contrast against the new background. So a phone number you styled grey can come back blue for a reader in dark mode even after you wrote the anchor yourself.

There is no reliable defence, and it is worth deciding that this is acceptable. A blue phone number is not a defect; a phone number nobody can tap is.

When to leave the detection alone

Auto-detection exists because it is useful. On a phone, a tappable number, a tappable address and a maps link are all things the reader may want. The strongest reason to intervene is not aesthetic: it is that the detector sometimes gets the number wrong, splitting an international format at the wrong place so the tap dials something invalid. Writing the anchor yourself with an explicit tel: href fixes the correctness problem and the colour problem at once.

Frequently asked questions