Apple has sent out an email to members of its Mac developer program reminding them that the deadline to implement sandboxing in their apps is still June 1st.

As a reminder, the deadline for sandboxing your apps on the Mac App Store is June 1. We’ve made the process easier with new sandboxing entitlements and APIs now available in OS X 10.7.3 or later and Xcode 4.3.2.

If you have an existing app on the Mac App Store that is not sandboxed, you may still submit bug fix updates after June 1. If you have technical issues that prevent you from sandboxing your app by June 1, let us know.

There are quite a few instances of Mac App Store apps already having implemented sandboxing in their apps. Password helper 1Password (which implemented it last September) and image editor Pixelmator among them.

Screen Shot 2012 05 18 at 3.05.54 PM 520x512 Apple sends out reminder to developers that Mac apps must be sandboxed by June 1st

Apple had previously set the sandboxing deadline for March 1st. By that time, developers that wished to continue selling their apps in the Mac App Store would need to abide by new rules that severely limited the areas of a computer that an app had access to. It later extended it out to June 1st.

Many developers, like Manton Reece and Daniel Jalkut, have recently expressed their dissatisfaction with the limited entitlements offered by sandboxing on the Mac.

Both Reece and Jalkut expressed their feelings that the current freedoms that developers have to access OS X are too limited and its not enough to have faith that Apple will make changes. “We can only make decisions based on what entitlements and APIs are there today,” said Reece “And today it’s not enough.”

Apple clearly wants the Mac App Store to be the primary way that people download apps on their Mac, but it also wants sandboxing to be the foundation of a more secure OS X.