..caution::

When you create a message withswiftmailer, itgenerate a Swift_Message

class. If the swiftmailer service is lazy loaded, itgenerate instead a

proxy class namedSwift_Message_<someRandomCharacters>.

When you create a message withSwiftMailer, itgenerates a``Swift_Message``

class. If the``swiftmailer`` service is lazy loaded, itgenerates instead a

proxy class named``Swift_Message_<someRandomCharacters>``.

If you use the memory spool, this change is transparent and has noimpart.

But whenyou usethe filesystem spool, the message class is serializedon

If you use the memory spool, this change is transparent and has noimpact.

But whenusingthe filesystem spool, the message class is serializedin

a file with the randomized class name. The problem is that this random

class namechange on every cache clear. So if you send a mail, then you

class namechanges on every cache clear. So if you send a mail and then you

clear the cache, the message will not be unserializable.

On the next ``swiftmailer:spool:send`` an error will raise because the

class ``Swift_Message_<someRandomCharacters>`` doesn't exist (anymore).

On the nextexecution of``swiftmailer:spool:send`` an error will raise because

theclass ``Swift_Message_<someRandomCharacters>`` doesn't exist (anymore).

The solutions are either to use the memory spool or to load the

swiftmailer service without ``lazy`` option (see:doc:`/service_container/lazy_services`).

``swiftmailer`` service without ``lazy`` option (see:doc:`/service_container/lazy_services`).