Apple - What's the 'followupd' in notifications?

This is part of the private CoreFollowup System Framework at

/System/Library/PrivateFrameworks/CoreFollowUp.framework/Versions/A/Support/followupd

There is no documentation about it, but the header files found at (that's for iOS, but I guess the framework is the same):

https://github.com/nst/iOS-Runtime-Headers/tree/master/PrivateFrameworks/CoreFollowUp.framework

don't show any evil things.

I suppose, it's for "following up" on notifications posted by other applications. There is an internal database of which the statements can be grabbed from the binary. It only contains title, body, some IDs and dates. Example:

INSERT INTO notifications (item_id, title, body, unlock_label, relevance_date, activate_action_id, dismiss_action_id, clear_action_id) VALUES (?, ?, ?, ?, ?, ?, ?, ?)

So, no – you should and cannot remove it.

[EDIT]

Regarding the icon. Some examples of system applications having that icon:

1. Go to AirDrop in Finder.
2. Set the setting to let 'no one' find you.
3. Don't send any files from iOS or other devices using AirDrop.
4. Restart Mac.
5. Gone.

I tested this with an iMac, a Mac Mini, and a Macbook Air 13. All restarted without followupd appearing any more.

I can recommend PhotoSync app to use instead to transfer files wirelessly which avoids this problem, and works between Mac, Windows, iOS and Android devices, making it a perfect solution for wireless transfer between multiple operating systems.

I am convinced it is AirDrop since it allows iOS devices to transfer files to OS X, because of the fact that when I AirDrop a file from my iPad or iPhone to the Mac, a notification banner and sound pops out from the right side of screen. Also, in Notification Center settings in OS X El Capitan, there is no AirDrop present to deactivate banners and sounds, and as soon as I AirDrop a file to Mac, followupd appears in the notifications again, with all settings reactivated to banners and sounds. Hence, even if you deactivate all tick boxes in followupd, as soon as you AirDrop to Mac from another device, it is instantly reinstated.