Online trolls are being urged to know where to draw the line after a Taranaki journalist was sexually taunted in the comments section of an article.

The journalist even had a threatening note dropped in her mailbox, after an opinion piece riled farmers into online abuse.

Rape Crisis Wellington spokeswoman Eleanor Butterworth says there's a sense of anonymity on the web.

"It's fine to challenge something, but when those comments are starting to talk about acts of sexual violence we have to see that as outside of normal reaction," she says.

Butterworth says comments condoning sexual violence clearly cross the line.

"It's intensely threatening, particularly when she's had notes through the letterbox. It has quite a different flavour to using an insult or calling someone a name."