An 18-year-old man was arrested in Abbots Langley after a number of schools and colleges across the UK received threatening emails.
The National Crime Agency (NCA) said the incident was linked to a hoax bomb threat that closed hundreds of schools in Hertfordshire and across the county last month.
The teenager was arrested in the village on March 28 on suspicion of making malicious communications.
A NCA spokesman said the threats had “caused considerable concern”.
He added: “We do not assess there to be an increased risk to the public.”
Around 400 schools were closed last month after receiving the emails.
A Hertfordshire Police spokesman said: “We believe this incident is linked to the hoax bomb threat that closed hundreds of UK schools last month.”
A 19-year-old man was arrested in Watford last month on suspicion of blackmail and making malicious communications after the hoax bomb threat.
Some of the Hertfordshire schools involved were Abbots Hill in Hemel Hempstead, Stanborough School in Watford, St Albans High School, Valley School in Stevenage, The Sele School in Hertford and Duncombe School in Hertford.