We are using SDL Tridion 2013 SP1 HR1. The EML files generated by outbound mailer service is contains Content-Type: text/html; charset="iso-8859-1" we want to remove charset="iso-8859-1" from Content-Type header.is there any setting in outboundemail configuration file to do it?
The encoding is determined by Chilkat based on the content. It is, unfortunately, a bit of a black box. Sometimes that detection fails and it picks the wrong encoding. That appears to be the case for you.
Luckily, we built in an override for just such a situation. You can set the
FixedEncoding element in OutboundEmail.xml to an encoding that will work for all of your e-mails (e.g. UTF-8).
Here is a link to the documentation page for the setting: Configuring outgoing e-mail