!!!IMPORTANT!!!
The following upgrading instructions are cumulative. That is,
if you want to upgrade from version A to version C and there is
version B between A and C, you need to following the instructions
for both A and B.
Minimal required version of the swiftmailer/swiftmailer library has been raised to 6.0.0.
You should adjust your program according to the change list for this version.
Since Swift_MailTransport has been removed in SwiftMailer 6.0.0, this extension now uses Swift_SendmailTransport by default.
Minimum version of PHP has been raised to 7.0.
