I’m using PHP mail and I have the following headers:
MIME-Version: 1.0
Content-Type: text/html; charset=UTF-8; format=flowed;
Content-Transfer-Encoding: 8Bit
X-Mailer: Pressflow
Errors-To: some@email.com
Return-Path: some@email.com
Sender: some@email.com
From: Some Email <some@email.com>
X-SMTPAPI: {"category":"key:some_key"}
Where some@email.com is a legitimate email, but I wouldn’t disclose it here…
Is there a way to modify this header such that my mail wouldn’t get sent to the spam folder in Outlook?
Look into SPF and DKIM. For an easier alternative, try email delivery services such as Mad Mimi or MailChimp.