Several Yahoo emails sent from iphone have disappeared
I have an iPhone 13 and use the mail app for Yahoo. In the last few months I have sent several emails from my phone that have completely disappeared (and were not received by the recipient). When this happened I had a good wi-fi connection. The emails are not in drafts, outbox, etc. How do I fix this? Note that this has not been a problem when using Yahoo on my computer.
iPhone 13, iOS 16