Email signature with a QR code on Android
Let us be blunt: Android mail apps only accept a plain-text signature. No logo, no QR code, no colours. This guide explains what to do instead, rather than letting you try for an hour.
The steps
Android apps only accept a plain-text signature: formatting and the QR code will not carry over.
The simplest route is to set your signature from a computer (Gmail web or Outlook web): most accounts then sync it to the phone.
Otherwise, type a text version including your card address.
The pitfall to know about
A signature composed on a computer stays intact in messages sent from that computer. On Android, use a text version containing your card's address: the link itself works everywhere.
Why put a QR code in a signature?
A professional sends several thousand emails a year, and each one shows their signature to someone. A QR code placed there leads to a business card whose contents can change at any time: you change number, the card follows, and the messages already sent stay correct.
Create yours, free
Pick the fields, the layout and the colour, copy, paste. Your logo is accepted on the free plan, and the QR code leads to a card you can edit whenever you like.