Package swiftmailer/swiftmailer is abandoned, you should avoid using it. Use symfony/mailer instead.

[croxton]

Description

composer depends swiftmailer/swiftmailer
wildbit/swiftmailer-postmark  3.3.0  requires  swiftmailer/swiftmailer (^6.0.0)  
yiisoft/yii2-swiftmailer      2.1.2  requires  swiftmailer/swiftmailer (~6.0)   

composer depends yiisoft/yii2-swiftmailer
craftcms/cms  3.7.23  requires  yiisoft/yii2-swiftmailer (^2.1.2) 

Looks like Craft / Yii and a number of transactional email plugins like Postmark depend on Swiftmailer, but it's due to be retired by the end of this month (November 2021). Any plans for this? https://github.com/swiftmailer/swiftmailer

Additional info

• Craft version: 3.7.23
• PHP version: 7.4
• Plugins & versions: craftcms/postmark

[thupsi]

Hello! There is a relevant discussion here