-There is a hook out there that checks the content of the email for
-keywords and warns you before the email is sent out if there's no
-attachment. This is currently work in progress, but you can already
-add the hook to your `~/.emacs.d/notmuch-config.el` file to test
-it. Details available (and feedback welcome) in the [relevant
-discussion](https://notmuchmail.org/pipermail/notmuch/2018/026414.html).
+Since version 0.29 Notmuch includes the `notmuch-mua-attachment-check`
+function. This function checks whether a message references an
+attachment and if it finds none it asks for confirmation before
+sending the message. The function is meant to be added to the
+`message-send-hook`, like so:
+
+ (add-hook 'message-send-hook 'notmuch-mua-attachment-check)
+
+The "customize"able variable `notmuch-mua-attachment-regexp` controls
+how reference to an attachment are identified. By default, it
+identifies English and French terms. For example, the following makes
+it recognise English and Portuguese terms:
+
+ (setq-default notmuch-mua-attachment-regexp
+ "\\b\\(attach\\|attachment\\|attached\\|anexo\\|anexado\\)\\b")
+
+
+## Avoid forgetting the subject
+
+It happens that we forget to enter the Subject line, particularly when
+we leave that to the end. It's easy to write a function that checks
+whether the Subject is empty, and add it to `message-send-hook` to get
+confirmation:
+
+ (defun my-notmuch-mua-empty-subject-check ()
+ "Request confirmation before sending a message with empty subject"
+ (when (and (null (message-field-value "Subject"))
+ (not (y-or-n-p "Subject is empty, send anyway? ")))
+ (error "Sending message cancelled: empty subject.")))
+ (add-hook 'message-send-hook 'my-notmuch-mua-empty-subject-check)
+