Add header X-Feed2Imap-GUID

3 files changed, 7 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7ededfd..4338b73 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- New header X-Feed2Imap-Guid
 
 ### Changed
 - Default for `min-frequency` is now 0 instead of 1.
diff --git a/internal/feed/mail.go b/internal/feed/mail.go
index a763ef8..0a8bd10 100644
--- a/internal/feed/mail.go
+++ b/internal/feed/mail.go
@@ -57,10 +57,13 @@ func (item *item) buildHeader() message.Header {
 	h.SetContentType("multipart/alternative", nil)
 	h.SetAddressList("From", item.fromAddress())
 	h.SetAddressList("To", item.toAddress())
+	h.Set("Message-Id", item.messageId())
 	h.Set(msg.VersionHeader, version.Version())
 	h.Set(msg.ReasonHeader, strings.Join(item.reasons, ","))
 	h.Set(msg.IdHeader, item.id())
-	h.Set("Message-Id", item.messageId())
+	if item.GUID != "" {
+		h.Set(msg.GuidHeader, item.GUID)
+	}
 
 	{ // date
 		date := item.DateParsed()
diff --git a/internal/msg/msg.go b/internal/msg/msg.go
index c71ddaf..a742a9d 100644
--- a/internal/msg/msg.go
+++ b/internal/msg/msg.go
@@ -12,6 +12,7 @@ const (
 	VersionHeader = "X-Feed2Imap-Version"
 	ReasonHeader  = "X-Feed2Imap-Reason"
 	IdHeader      = "X-Feed2Imap-Item"
+	GuidHeader    = "X-Feed2Imap-Guid"
 )
 
 type Messages []Message