When I write e-mails in Japanese, I make it a point of writing my name, first name only if it's someone I know a little, in roman letters. This is done deliberately by me to position and remind the Japanese person that I'm not Japanese (making them go "oh, look how good Japanese he can write" and not "this guy obviously can't string a proper sentence together, he needs to go back to school") which might be the case if I would sign off with only my Japanese family name.
However, lately this has caused significant variations in the e-mails with a new partner company I'm corresponding with. For the sake of it, say my name is "Tomas Yutani (湯谷)" and I sign the mails with "Tomas". Over the course of three responses from my Japanese counterpart, he first started with "Dear Mr. Tomas", then, the next time followed by Tomas様 (the courtesy "san" in chinese characters) and then latest 湯谷 様 completely in Japanese. It seems like he is going for a gradual shift to Japanese on me, but I'll keep signing off with "Tomas", I won't yield!