Question about iphone mail

I use Outlook for mac to send emails. I'll compose an email from my computer and send it and it'll have the company logo in my signature. If someone replies from an iphone or ipad, the signature disappears and the font is different. This happens if someone sends me an email and I reply from my iphone and once the apple device is introduced into the email convo, the font and signature is thrown off for as long as that email chain is around, even if I start replying from my computer again. Why does this happen and is there a way to avoid it?

Am no font expert by any stretch of the imagination, but my first guess would be you're using a font not available in iOS.

That makes sense, but it doesn't put it into a font that is a standard ios font, either.