# possible variables you can use.
#mail_log_prefix = "%s(%u): "
-# Format to use for logging mail deliveries. You can use variables:
+# Format to use for logging mail deliveries:
# %$ - Delivery status message (e.g. "saved to INBOX")
-# %m - Message-ID
-# %s - Subject
-# %f - From address
-# %p - Physical size
-# %w - Virtual size
+# %m / %{msgid} - Message-ID
+# %s / %{subject} - Subject
+# %f / %{from} - From address
+# %p / %{size} - Physical size
+# %w / %{vsize} - Virtual size
+# %e / %{from_envelope} - MAIL FROM envelope
+# %{to_envelope} - RCPT TO envelope
+# %{delivery_time} - How many milliseconds it took to deliver the mail
+# %{session_time} - How long LMTP session took, not including delivery_time
+# %{storage_id} - Backend-specific ID for mail, e.g. Maildir filename
#deliver_log_format = msgid=%m: %$