To be honest it's hard to know as it'll depend if the block was put on at your Internet account end, or in your mail program. And even then there are different ways to do it such as rejecting the connection, bouncing or just auto deleting.
If you want to be sure, you could send an e-mail to
trev @ beammeupnowplease.com (removing spaces) with the address of the problem person and I could send it a fake email apparently coming from them and report back here with the result, assuming it bounces at all. Best make the subject something mentioning AB if you do.
Just remember not to post their e-mail address here as that breaks AB site rule 3.
Can't really think of another way to test it or to know for sure, although you could fake it yourself by altering the settings in your e-mail program.
Trev