Low space even though most apps are linked to SD card I have link2SD and 90% of the apps are on the SD card. Yet I still only have a few MB left of space. I tried refreshing my e-mail and got a message "can't download more e-mails, delete some first". I connect using IMAP. What can I do? Obviously I don't want to delete a whole bunch of e-mails but is there a way to have only the 50 most recent e-mails sync to the phone?

Are there other places space could be taken up? When I started running low I went to the app manager but the system mail app wasn't included there so it confused me as to what was taking up all the space (I'm still just guessing it's e-mail).
This sounds a lot like an issue with cache. While the apps themselves can be stored on the SD card, cache that they produce might not. As I don't know what apps you actually have, I can only advise you to at least try and delete cache from various apps, such as twitter, facebook etc.

To delete cache, do as follows (this is for android 4.3): Settings -> More -> Application manager

Here you should be able to click in on every installed app, and delete their cache. Beware, tho, for something like calender and alarm clock apps, any set up serviced from them might reset! This should not, however, delete the app itself.