The vote-administration knows only who voted what, if they know who is behind the data communications channel through which you (voter) were send the vote-code you need to vote.
If the voters are registered anonymously, for instance using a paper ballot cast of anonymous e-mail accounts - essentially "voting for yourself" - then the vote-administration has no way of knowing who is behind a ballot. The anonymity of the vote is then equal to what the paper-ballot registration afforded.
When not using "double blind" anonymity, the vote-administration knows better who is behind each (or some of the) ballot(s). (This means the vote-correction process can be more secure (see previous intro).)
When it does not matter if the vote-administration can know who voted what, and if voters do not mind being known as voters, lists of voting voters for each poll can be created. This will make sure it is difficult to add false voters to the poll, a problem which is more significant for fully anonymous voting. For fully anonymous voting, group totals will need to be known by voters to reduce this danger.