Your message was sent but a copy was not placed in your sent folder
Your message was sent but a copy was not placed in your sent folder (Sent Mail) due to network or file access errors. You can retry or save the message locally to Local Folders/Sent Mail-nielscorfield@gmail.com.
Am getting this, and similar error messages repeatedly
Any suggestion gratefully received
Opaite Mbohovái (2)
Gmail automatically copies sent messages to Sent Mail, so 'Place a copy in' in the Copies & Folders section of Account Settings should be unchecked. Doing so usually eliminates the error.
sfhowes answer is exactly right! I've been frustrated with this same problem for weeks. Finally found sfhowes answer and it solved the problem. Thank you!!