A FETISH website member called Architect72 sent an email to an address used by Elaine O'Hara saying they hoped she was "not suffering too much on the inside," the jury in the trial of Graham Dwyer heard.
The message from an email address linked to a profile on the Alt.com site was sent to an email address Ms O'Hara had been using in 2008.
It was among a number of messages retrieved by gardai who examined Ms O'Hara's computers after her disappearance and death.
Dated September 19, 2008, the sender said: "I hope you are keeping ok.
"I've assumed you are trying to get better and trying to stay away from what we do together. Just so you know, I'm always thinking of you and hoping you are safe and not suffering too much on the inside."
The sender also told her that he or she would do what they promised to do "regardless of the consequences", adding that "all you have to do is call me from a phone box and say where and when".
Reading from the mail, Prosecutor Sean Guerin SC said the author added that it was "for a chat or the harmless things you liked to do", and it doesn't matter if the call is "years away".
The jury was told the message was sent from the email address firstname.lastname@example.org, which the court would hear "in due course" was the address of Architect72.
It was sent to email@example.com, an address being used at the time by Ms O'Hara.
A trace of a partial message from fetishboy was also recovered and said: "Hi again, I'm heading down the country for the weekend, have a good one yourself, If you are ...".
Another, from November 1, 2007, included references to "fetish boy", "cutting myself" and a punishment with master's scalpel, Det Gda Brid Wallace confirmed.
The jury heard the Alt.com profile Submissive391 viewed another profile name Architect77 on October 25, 26 and 31 in 2007, then again on November 7 and 11 that year.
The court also heard that a trace of contacts in Ms O'Hara's eircom.net email account had references including firstname.lastname@example.org, email@example.com, firstname.lastname@example.org and one in her father's name.
Google searches were found for the terms "Graham Dwyer architect" and "Wejchert".