Retrying to send fail messages (enh)

[sazanof]

Hello everyone! I will be glad if you consider this improvement and give your comments. =) Maybe it refers to https://github.com/nextcloud/mail/issues/6401

Basically there are 2.5 improvements:

• Batch sending of emails with the failed status
• • The interface for sending a single message has been slightly redesigned
• Background sending of emails with the failed status when the page loads

And here are the screenshots:

Perhaps another processing logic is needed here, so I would like to discuss this. Thanks!