I just tested it, and it will fail if the client (`@gmail`) switches to the mailbox using `EXAMINE`, which is what is used when `read_only` is true.  It raises this error:

`Net::IMAP::NoResponseError: EXPUNGE attempt on READ-ONLY folder`

Rather than try to put logic around all of the operations that we would expect to error with read only set to true, I wanted to fallback on the standard `Net::IMAP` errors.