Can you save attachments to the SD card? Or will I have to use a different email app.
I think a different app. I use Kaiten mail, (US$5). It has a ton of benefits over the default, (and most other mail clients) including the ability to save attachments AND even the mail data to wherever you want, including the external card. Kaiten is a super set of K-9 which is free and if I remember correctly could also specify the default attachment storage location.
Using the Stock email app on my Note, there is a little icon to the right of the attachment thatI looks like a little letter. Press this and it saves the attachment into the download folder, on the internal memory. You could use the My Files app to move it to external SD card. I checked around for settings to change where the files could be moved to, but could not find one. I was only checking in the settings of the stock email app. I will browse around in the off phone settings.