The Department of Corrections has set up a phone number 0800 345 006 and a dedicated email address firstname.lastname@example.org for people to report any concerns they have about receiving unwanted correspondence from prisoners.
The department says that over the last week a number of concerns have been raised about how it manages prisoner mail.
"We take our responsibility for safety very seriously, and on this occasion we have not met our own high standards."
Corrections says both the email and 0800 number are staffed on weekdays only. Voice messages can be left after hours and staff will respond.
"Corrections has also put in place a number of steps to ensure this doesn’t happen again. The mail of prisoners who have been identified with extremist ideologies and/or registered victims will be immediately centralised pending a full review carried out by an external party."
The department says it will remain this way until the review has concluded the new process in place will prevent this from ever happening again.
"This has also highlighted the need for us to look at the current legislation and how it is being applied and whether it is fit for purpose. We are currently providing further advice to the government on this point."