HTML Email Signature Compatibility

I’m currently designing an HTML email signature to include my company’s logo, contact information and a slogan. The issue is that they would like it to look the same in desktop email clients (Outlook, etc.) and mobile devices (such as BlackBerry’s). I’ve spent the last while researching ways in which you could maintain the same layout and avoid wrapping / line breaks but so far I have not found anything (even on Sitepoint).

Does anyone know of a way to prevent the signature from wrapping, or if you can inherit the default font-size of the device?

Trying to get the same appearance in all e-mail clients is a massive exercise in futility. Frankly, using anything for formatting fancier than plaintext just screams “I’m a spammer” or “accessibility, what’s that?”

See why I have my server set up to reject e-mails with HTML in them!