Good morning Ruth.
Maybe you should try to post your question joinin' a Yahoo's forum.
But I'll give you my point of view. I assume that you're using Apple Mail app to send all your e-mails, with two mail accounts: Yahoo and iCloud.
Should be this case, as I told you in my previous answer, considering that:
- you've lost the swish sound sending a Yahoo mail message (which I think has nothing to do with notifications) after the yahoo app's update;
- you didn't change anything in Settings>Sounds>Sent mail>Swish;
- you can hear the swish sound, using iCloud mail account;
then I think there's something changed in the Yahoo update.
On the contrary, if you use the Yahoo app (and not Apple Mail app) to send yahoo mail messages, you should check other (new?) settings in Yahoo app, but I can't imagine what you should check.
Please keep me informed.
Regards
Giulio