I have read many articles on Swiftmailer having a common issue of becoming very slow when using SMTP for NUMEROUS reasons. Something that occurred to me is to spool the mail off to memory or a directory as described here ( https://symfony.com/doc/2.6/cookbook/email/spool.html ). The hope is that this approach within MachForm would immediately return the user to a refreshed page rather than wait for the SMTP transaction to complete as MachForm would see the transport as completed when spooled -- then have a cronjob or other that that monitors a directory and sends the mail out. How/where within MachForm (and/or the lib/swift-mailer directory) would I look at to accomplish this?