Nautilus-sendto is putting the name unquoted in the To field of the mail when trying to send a file. For example, if I send one two myself, it will put: Blandford, Jonathan <jrb> on the To line. Because of the comma, this will send mail to "Jonathan <jrb>" and Blandford, which will bounce.
This only happens when you enter an e-mail address with a name, but not using completion. Fixed upstream. 2008-03-26 Bastien Nocera <hadess> * src/plugins/e-contact-entry.c: Update from SVN and fix a warning * src/plugins/evolution.c (send_files): Quote the e-mail address we pass to evolution, as some people might use "Surname, Name <address>" instead of just "address" (Closes: https://bugzilla.redhat.com/show_bug.cgi?id=438695)