As of 2010, a majority of mail user agents did not follow this prescription fully. The widely used Mozilla Thunderbird mail client ignores the content-disposition fields in the messages and uses independent algorithms for selecting the MIME parts to display automatically. Thunderbird prior to version 3 also sends out newly composed messages with inline content disposition for all MIME parts. Most users are unaware of how to set the content disposition to attachment. Many mail user agents also send messages with the file name in the name parameter of the content-type header instead of the filename parameter of the header field Content-Disposition. This practice is discouraged, as the file name should be specified either with the parameter filename, or with both the parameters filename and name.
As of 2010, a maj.ority of mail user agents did not follow this prescription fully. The widely used Mozilla Thunderbird mail client ignores the content-disposition fields in the messages and uses independent algorithms for selecting the MIME parts to display automatically Thunderbird prior to version 3 also sends out newly composed messages with inline content disposition for all MIME parts. Most users are unaware of how to set the content disposition to attachment. Many mail user agents also send messages with the file name in the name parameter of the content-type header instead of the filename parameter of the header field Content-Disposition. This practice is discouraged, as the file name should be specified either with the parameter filename, or with both the parameters filename and name.