Watch for IP Used to Contact Sublime
$ sudo netstat -nputwc | grep subl
Example Output:
tcp 0 0 10.211.55.6:46296 45.55.255.55:80 ESTABLISHED 337/sublime_text
tcp 0 0 10.211.55.6:46296 45.55.255.55:80 ESTABLISHED 337/sublime_text
Block with iptables
$ sudo iptables -A OUTPUT -j DROP -d 45.55.255.55
List your iptables
$ sudo iptables -S
Older Methods No Longer Work
Refer: https://stackoverflow.com/questions/35269327/how-to-disable-new-version-notifications/35269421
go to Preferences -> Settings-User and add there: "update_check": false
EDIT :
If it's not working then add this line 127.0.0.1 www.sublimetext.com in your host file
File Location
Windows : c:/windows/system32/drivers/etc/hosts
Linux : /etc/hosts

Remove com.techsmith.snagit.plist -----------------------
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1.) Close Snagit and confirm its not running by accessing Activity Monitor. Look for Snagit in the running list of applications.
2.) Click on your Finder and then click the Go menu at the top. Hold down the Option key on your keyboard and choose the Library item in the Go dropdown. Then go to Preferences.
3.) Locate all com.techsmith.snagit.plist files and move them to your trash (there may be one with a 4 in it too)
4.) Confirm that com.techsmith.snagit.plist is no longer in the Preferences folder.
5.) Reboot the computer and try Snagit again.
Please let me know if you have any questions.
Kind Regards,
Jason
Technical Support Specialist