A resident's e-mails objecting to a planning application were blocked by a computer system that tries to filter blue or risque language.
The IT system filtered the word erection
Commercial lawyer Ray Kennedy, from Middleton, Gtr Manchester, wrote three e-mails to Rochdale Council complaining about a planning matter.
But two messages, with the word "erection", were blocked as offensive and the third was too late.
The council said it would be apologising to Mr Kennedy.
Mr Kennedy's third e-mail, containing the same word, somehow sneaked past the cyber prude but a planning officer told him his next-door neighbour's proposals had already been given the go ahead.
The software used by Rochdale Council is designed to filter out any obscene material and views the word "erection" - used by Mr Kennedy in the context of building an extension - as a sexual term.
Mr Kennedy, who lives on Sunny Brow Road, is considering complaining to the local government ombudsman over the blunder.
A Rochdale Council spokesman said: "The software that protects the council's e-mail system from spam and other offensive material is not designed by the council and we do not control which words are blocked.
"We will be writing to the resident to apologise for the failure of his e-mails to get through."