Minor fix

src/internal/m365/collection/groups/conversation_handler.go

@@ -19,15 +19,19 @@ var _ backupHandler[models.Conversationable, models.Postable] = &conversationsBa
 type conversationsBackupHandler struct {
 	ac                api.Conversations
 	protectedResource string
+	// SMTP address for the group
+	resourceEmail string
 }
 
 func NewConversationBackupHandler(
 	protectedResource string,
 	ac api.Conversations,
+	email string,
 ) conversationsBackupHandler {
 	return conversationsBackupHandler{
 		ac:                ac,
 		protectedResource: protectedResource,
+		resourceEmail:     email,
 	}
 }
 
@@ -120,13 +124,17 @@ func (bh conversationsBackupHandler) getItem(
 	containerIDs path.Elements, // expects: [conversationID, threadID]
 	postID string,
 ) (models.Postable, *details.GroupsInfo, error) {
+	cc := api.CallConfig{
+		Expand: []string{"inReplyTo"},
+	}
+
 	return bh.ac.GetConversationPost(
 		ctx,
 		groupID,
 		containerIDs[0],
 		containerIDs[1],
 		postID,
-		api.CallConfig{})
+		cc)
 }
 
 //lint:ignore U1000 false linter issue due to generics
@@ -134,6 +142,13 @@ func (bh conversationsBackupHandler) augmentItemInfo(
 	dgi *details.GroupsInfo,
 	c models.Conversationable,
 ) {
+	// Posts are always sent to the group email address, along with additional
+	// recipients if any. Currently we don't have a way to get the unique
+	// recipient list for individual posts due to graph api limitations.
+	//
+	// Store the group mail address so that we can use it to populate the 'To'
+	// field during Post -> EML exports.
+	dgi.Post.Recipients = []string{bh.resourceEmail}
 	dgi.Post.Topic = ptr.Val(c.GetTopic())
 }
 

src/internal/m365/service/groups/backup.go

@@ -3,6 +3,7 @@ package groups
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/alcionai/clues"
 	"github.com/kopia/kopia/repo/manifest"
@@ -319,10 +320,17 @@ func backupConversations(
 	counter *count.Bus,
 	errs *fault.Bus,
 ) ([]data.BackupCollection, error) {
+	groupEmail := strings.Clone(ptr.Val(bc.group.GetMail()))
+	// This is unlikely, but if it does happen in the wild, we should investigate it.
+	if len(groupEmail) == 0 {
+		return nil, clues.New("group has no mail address")
+	}
+
 	var (
 		bh = groups.NewConversationBackupHandler(
 			bc.producerConfig.ProtectedResource.ID(),
-			bc.apiCli.Conversations())
+			bc.apiCli.Conversations(),
+			groupEmail)
 		colls []data.BackupCollection
 	)
 

src/pkg/backup/details/groups.go

@@ -61,11 +61,13 @@ type GroupsInfo struct {
 }
 
 type ConversationPostInfo struct {
-	CreatedAt time.Time `json:"createdAt,omitempty"`
-	Creator   string    `json:"creator,omitempty"`
-	Preview   string    `json:"preview,omitempty"`
-	Size      int64     `json:"size,omitempty"`
-	Topic     string    `json:"topic,omitempty"`
+	CreatedAt  time.Time `json:"createdAt,omitempty"`
+	Creator    string    `json:"creator,omitempty"`
+	Preview    string    `json:"preview,omitempty"`
+	Recipients []string  `json:"recipients,omitempty"`
+	InReplyTo  string    `json:"inReplyTo,omitempty"`
+	Size       int64     `json:"size,omitempty"`
+	Topic      string    `json:"topic,omitempty"`
 }
 
 type ChannelMessageInfo struct {

src/pkg/services/m365/api/conversations.go

@@ -69,8 +69,25 @@ func (c Conversations) GetConversationPost(
 		preview = "malformed or unparseable content body: " + preview
 	}
 
+	var inReplyToID string
+
+	prevPost := post.GetInReplyTo()
+	if prevPost != nil {
+		inReplyToID = ptr.Val(prevPost.GetId())
+	}
+
+	// Set prev post to nil to avoid storing it again in the backup. Storage is unnecessary
+	// since this is a read only property and graph doesn't support POSTing it. This is
+	// also safe to do since we do a full enumeration every time, so post and all its
+	// ancestors are guaranteed to exist.
+	//
+	// All we need to persist here is the prev post ID here so that we can build the
+	// reply tree during restore operation and restore posts top to bottom using
+	// POST /groups/{id}/conversations/{id}/threads/{id}/posts/{id}/reply
+	post.SetInReplyTo(nil)
+
 	if !ptr.Val(post.GetHasAttachments()) && !HasAttachments(post.GetBody()) {
-		return post, conversationPostInfo(post, contentLen, preview), nil
+		return post, conversationPostInfo(post, contentLen, preview, inReplyToID), nil
 	}
 
 	attachments, totalSize, err := c.getAttachments(
@@ -95,7 +112,9 @@ func (c Conversations) GetConversationPost(
 
 	post.SetAttachments(attachments)
 
-	return post, conversationPostInfo(post, contentLen, preview), graph.Stack(ctx, err).OrNil()
+	return post,
+		conversationPostInfo(post, contentLen, preview, inReplyToID),
+		graph.Stack(ctx, err).OrNil()
 }
 
 // ---------------------------------------------------------------------------
@@ -105,7 +124,7 @@ func (c Conversations) GetConversationPost(
 func conversationPostInfo(
 	post models.Postable,
 	size int64,
-	preview string,
+	preview, inReplyToID string,
 ) *details.GroupsInfo {
 	if post == nil {
 		return nil
@@ -120,6 +139,7 @@ func conversationPostInfo(
 		CreatedAt: ptr.Val(post.GetCreatedDateTime()),
 		Creator:   sender,
 		Preview:   preview,
+		InReplyTo: inReplyToID,
 		Size:      size,
 	}
 

src/pkg/services/m365/api/conversations_test.go

@@ -109,7 +109,7 @@ func (suite *ConversationsAPIUnitSuite) TestConversationPostInfo() {
 			t := suite.T()
 
 			post, expected := test.postAndInfo()
-			result := conversationPostInfo(post, 0, "")
+			result := conversationPostInfo(post, 0, "", "")
 
 			assert.Equal(t, expected, result)
 		})