Do you mean "monkey tail" ("apenstaart")? I forgot about that one. I haven't heard it in years in Belgium.

I'm not so sure. I'm Dutch as well, and when I recite my email address I use the English "at", so "douwemaan at domain" rather than the unwieldy (4 syllables long!) "douwemaan apenstaartje domain".

In my experience most (if not all) people in my age group (18 - 25) simply pronounce it as "at". This could be a generational thing as most of us were raised with the internet and all these internet-y terms come quite naturally to us.

Generally for email we say "at", because it's just shorter. But for other uses, "apenstaartje" is also in widespread use. In particular for referring to the symbol itself, because it avoids ambiguity.