removed unused code inherited from version 4.0

[SergiuBota1]

Removed unused code inherited from version 4.0
close #70

Removing unused code also fixed phpcs erros for mail.global.php.dist
close #72

[alexmerlin]

Just to confirm, according to the mailer CHANGELOG:

• auth_mode has been removed in version 4.4.0 - this was the equivalent of our connection_class config (as mentioned in the old mailer docs)

[alexmerlin]

FYI, besides regular SmtpTransport there is also EsmtpTransport, which seems to add many enhancements to the SMTP protocol. Comparison here: https://www.geeksforgeeks.org/what-is-esmtp-extended-simple-mail-transfer-protocol/

[alexmerlin]

Some final tweaks... 🤞

[alexmerlin]

@arhimede Also note that since version 6.2, symfony/mailer has a command for sending test emails that might come handy when testing mail configurations.