Make sure that when carrying out Step 1 you are NOT using Safari as this causes the styles to copy incorrectly (try Chrome or Firefox instead)
1. Send a blank email with the new HTML signature to your iPhone.
2. Open the email you sent to your iPhone. Find a part of the signature text that is not a web or email link. Press and hold this text. The context menu will appear over the text. Tap Select All, then Copy.
3. Go into the iPhone email signature editor by going to Settings > Mail, Contacts, Calendars > Signature.
4. Delete any plain text email signature you might already have, press and hold the screen until the context menu appears and select Paste.
5. The new email signature will now appear in the editor. The original formatting will have been lost and it will appear slightly altered – this is normal - iOS automatically adds its own coding to the HTML source of the email signature.
6. All you have to do is shake your iPhone to trigger the Undo Change Attributes context menu and select Undo. (Yes, you must shake your iPhone for this context menu to appear) You’ve now successfully removed the additional iOS formatting.
7. You’ll want to test it to make sure the iOS formatting was removed.
Some email clients need email signatures as an HTML file or source code. Click on the "copy HTML" below