Renfrewshire Council wrote to the 5354 people on its approved landlords list inviting them to a Landlord Accreditation training course, but also attached a list containing their personal details.
The error is a breach of the Data Protection Act and one dad, who rents out a home in Renfrewshire, is fearful that the nature of his job could put him at risk of attack by animal rights activists.
The man, who did not want to be named, works for a major pharmaceutical company.
He said: "When I saw the email, I noticed a spreadsheet attached, which I naturally opened. When I realised what it was, I was shocked. It contains the personal details of thousands of landlords.
"I emailed the council right away to say I was extremely disappointed and anxious for the security of my family as a result of this breach of the Data Protection Act.
"I work for a pharmaceutical company and we are at a higher risk of attack from animal rights extremists.
"What the council did was release my email address, containing my company name, into the public domain along with my home address."
Renfrewshire Council replied to the man's complaint and apologised for the error. A probe is under way to find out what went wrong and to ensure it doesn't happen again.
A Renfrewshire Council spokesman said: "We recognise the spreadsheet should not have been circulated in this way and that it also contained information which is not in the public domain.
"The council deeply regrets this accidental release of personal information.