One potential cause for the poor reception of your remarks - quite apart from "I expect you to" and "Please do so" which are both rather hectoring and apparently critical - is the use of the cc function to involve other people.

If you were unaware, cc is an abbreviation for "carbon copy": traditionally people who needed to know about the contents of a paper memo (pre e-mail, but the same connotation still exists) but were not necessarily expected to take part in the conversation, would receive a carbon copy of the original document rather than a typed original. Using cc to notify other people of an exchange says - especially given the wording of your e-mail - that you need them to know that your colleague is failing, needs to be reprimanded and that no fault attaches to you for this as he has failed to meet your expectations (despite the fact you are not his manager) and that you have now issued him with an ultimatum.

If my manager - let alone a colleague - had done that to me I would have been utterly livid and considered raising a formal complaint with the HR department and demanded - at the very least - either a retraction to the 10 people on the cc list or a clarification.

Language can be a tricky thing, but try to imagine someone sending an e-mail to you, copying in 10 of your co-workers, saying "you have seriously disappointed me, get off your backside and get things done rather than sitting around ignoring the situation. I expect you to comply with my instructions." Especially if it came not from your boss but from a colleague. It's a bit grim, isn't it?

Don't beat yourself up over it but perhaps find a trusted colleague with good language skills to be a proofreader before your send out mas-receipt e-mails again.

One potential cause for the poor reception of your remarks - quite apart from "I expect you to" and "Please do so" which are both rather hectoring and apparently critical - is the use of the cc function to involve other people.

If you were unaware, cc is an abbreviation for "carbon copy": traditionally people who needed to know about the contents of a paper memo (pre e-mail, but the same connotation still exists) but were not necessarily expected to take part in the conversation, would receive a carbon copy of the original document rather than a typed original. Using cc to notify other people of an exchange says - especially given the wording of your e-mail - that you need them to know that your colleague is failing, needs to be reprimanded and that no fault attaches to you for this as he has failed to meet your expectations (despite the fact you are not his manager) and that you have now issued him with an ultimatum.

If my manager - let alone a colleague - had done that to me I would have been utterly livid and considered raising a formal complaint with the HR department and demanded - at the very least - either a retraction to the 10 people on the cc list or a clarification.

Language can be a tricky thing, but try to imagine someone sending an e-mail to you, copying in 10 of your co-workers, saying "you have seriously disappointed me, get off your backside and get things done rather than sitting around ignoring the situation. I expect you to comply with my instructions." Especially if it came not from your boss but from a colleague. It's a bit grim, isn't it?

Don't beat yourself up over it but perhaps find a trusted colleague with good language skills to be a proofreader before your send out mass-receipt e-mails again.