If order doesn't matter (i.e. just exclude all emails with an md5 in the exclude file) and you're not wedded to awk, use [`join`][1]:

 join -v 1 -j 1 <(sort emails) <(sort excludes)

`-v 1` tells it to print lines in the first file (emails) that don't have a corresponding line in the second file (excludes). 
`-j 1` tells it to only look at the first column of each. 


 [1]: http://compute.cnr.berkeley.edu/cgi-bin/man-cgi?join


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If you want to use awk, I believe this should work:

 awk 'NF==1{exclude[$1]++} NF==2&&!exclude[$1]' excludes emails

Or if the two files correspond line-by-line and you only want to exclude, e.g. line 2 if both have the same hash on that particular line, use this:

 awk 'NF==1{hash[FNR]=$1} NF==2&&hash[FNR]!=$1' excludes emails