Originally Posted by AGGRAVATED
What is going on the Incredible. Cannot sync mail and have the infamous Error Low on Space - Phone storage space is getting low.
You're gmail isn't syncing BECAUSE of the low on space issue. There is another thread stickied on top of the support subsection about this.
Long story short, go the the apps list in the Manage Applications menu, clear cache and data from the larger apps (you can sort the list by size), and if you're on Gingerbread you can move applications to the sd card to make more room (if they are already on the sd card you can move them back to the phone and then back to the SD card). You can also delete apps outright.
The problem is a partition android uses to store private application data fills up. The goal is to remove some of that data. There is also a permanent fix you can apply if you are rooted.