TYPO3 Core

Both spools iterate over all currently queued mails and concatenate these.

Using a spool because of async sending and the resulting performance is not good.

Using the FileSpool and sending mails to 1000+ recipients results most of the time in a browser timeout. The toString is called indirectly through the AbstractTransport class as a representation for the transports name.

To regain performance and be compatible we need to cleanup toString() to just return an identifier instead of the whole queue.