Hi,
I have the same problem so I have got a look in the code, appears to me that the function who encodes 'From' field execute his operations on whole string composed by nickname <mail@domain.ext>
so it puts in the header the result From: =?UTF-whatever...blabla_=?
, in this case when header is passed to the PEAR function who is entitled to process data and send it to server you have as result that someone (PEAR or SMPT I don't know) add the domain extension to this field resulting in a field of the type =?UTF-whatever...blabla_?=@domain.ext
in this case this is not a well formatted 'From' field and we can see the results of this in our recipents mail client, a correct 'From' field is kind From: =?UFT-whatever..blabla?=
, I have modified the txtHeaders function in lib/Mail/mime.php to take care of these considerations, it takes 'From' field from array with only the nickname who eventually should be encoded, than, after add your mail address with a straight copy, it seems to work but I don't know if the encoding of whole 'From' field is necessary (mail address with specialchars perhaps?)
My configuration is SMTP Postfix, PHP 4.4.4.