CookieRevised, raceprouk and any others that have posted that block checkers are not reliable and do not work are correct.
A long time ago, there was a bug in the protocol that allowed these block checkers to see what someone's real status was. If the status was online, and the contact displayed as offline, then you would know that you were blocked. CookieRevised was correct about that; it did not check if you were 'blocked', it merely checked the status you had set.
Now there is an option to only allow people on your allow list to see your status and send you messages. If this option is on, block checkers will always detect that contact as being offline, even if he/she is in fact online: simply because the block checker is not on your allow list.
When we say the bug has been fixed, we mean that block checkers could get past that option a long time ago and still show your real status, even if they were not on the allow list, but now that has been fixed, they can't get past it anymore.
Everyone can easily verify this for themselves: check the box (it's on the Privacy tab at the Options you can set in the menu Tools) and use block checkers - for example the program Duane_Bale attached to his/her post: make sure your status is set to online and enter your own email address.
You will see it shows you as offline, though you know you are online
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