I’m pretty sure sending login information (username, password) to clients in a plain email is not very safe.
First, why not? I’m not sure how packet sniffing (if that’s what the insecurity is) works, or whose computers (other than my cable companies and various ISPs) will see/pass on the packets.
Second, is it safe simply put the needed information in a Word or Zip file and send it as an attachment, or can sniffers look inside those as well? How best to send such information when phoning/faxing is not an option and clients aren’t very sophisticated? These aren’t nuclear secrets, but malicious use of the information could result in hours of headaches.