Conversations
Webmail groups a message and its replies into one conversation, the way most mail apps do. You read the whole exchange in one place, and the folder list counts conversations, not single messages.
In the message list
Each row is one conversation. It shows:
- who took part, with "me" for you;
- how many messages it holds (the small number);
- the newest message's subject, preview and time.
A row is bold while any of its messages is unread, and starred when any of them is starred.
Reading a conversation
Opening a row shows every message of the conversation, oldest first. That includes your own replies from Sent. Messages you have read are folded to one line, except the newest. Click a folded line to open it, and click the sender of an open message to fold it again. Unread messages and drafts are always shown open, and opening the conversation marks them read.
The toolbar at the top acts on the whole conversation in the folder you are in:
- Archive, Junk, Delete and Move to… take the conversation's messages out of this folder. Copies in other folders, such as your replies in Sent, stay where they are.
- Delete forever, in Trash, deletes the conversation's messages in Trash.
- Reply, Reply all and Forward answer the newest message.
- Mark unread marks the newest message unread.
When a conversation has more than one message, each open message has its own small buttons: reply, reply all, forward, star, and Source and headers. A draft reply shows Edit draft.
Messages in Trash or Junk are left out of a conversation unless you are in that folder. Very long conversations show their newest 100 messages.
How messages are grouped
A message joins a conversation when both of these hold:
- it names an earlier message in your mailbox as the one it answers (the In-Reply-To and References headers that every mail app sends with a reply), is named by one, or has the same Message-ID;
- its subject matches once "Re:", "Fwd:", "AW:", "SV:", list tags such as "[team]", and case and extra spaces are ignored.
So a reply whose subject was changed starts a new conversation, and so does a new message that only happens to share a subject.
Grouping is per mailbox. Your conversations are built only from your own messages and are never visible to anyone else, even when they answer the same mail.
Mail that was delivered before this feature arrived keeps one conversation per message.
Turning it off
Go to Settings and switch off Group messages into conversations. The list then shows one row per message, and opening a message shows only that message. The setting is kept in this browser.
For developers
This is standard JMAP threading (RFC 8621). threadId on every Email, Thread/get, collapseThreads on Email/query, and totalThreads and unreadThreads on each Mailbox all work. A conversation's id never changes. When a reply arrives before the message it answers, both join the reply's conversation, and conversations are never merged afterwards.