'Tried to read a line' error means, that there was a timeout or the connection was cut.
In most cases this error means that the connection was interrupted, it was lost, the server disconnected or your antivirus/firewall cut the connection.
In technical terms, it means exactly what the exception’s message says:
Component tried to read a line (ending with CRLF), the line was expected in accordance to the protocol in use (IMAP in your case), but it has not been received during the specified time period.
On extremely slow networks you may increase timeout values: ReceiveTimeout and SendTimeout (defaults are set to 20 seconds).
In most cases you’ll need to connect again.