fix MimeMessage::formatAddress not protecting recipient names

[Plaristote]

Greetings !

Right now, trying to send an email, to someone whose name contains a comma, results in a ClientError. According to the following topic :

https://stackoverflow.com/questions/15555563/how-to-format-an-email-from-header-that-contains-a-comma

... it seems that to prevent this issue, names in mail headers should be escaped using double quotes. This pull request achieves this result using stringstream and some iomanip magic. It does imply a back-and-forth conversion between QByteArray and std::string... but I don't believe Qt provides their own implementation for something like std::quoted, so this seemed like the simplest way to reach the goal.

[attila-tokes]

@Plaristote, have you tried to set the header encoding to QuotedPrintable or Base64? If the special character are only in the recipient's name (and not in the email address), it should resolve this problem.

[bluetiger9]

Hi @Plaristote! 🙂

Checked today, and using , in names works with MimePart::Encoding::Base64.

With MimePart::Encoding::QuotedPrintable commas were not escaped by default. I made a fix in 014970d, and now QuotedPrintable works too.

Using the default _8Bit encoding is usually not a good idea arbitrary names and headers. For now I will not add escaping as QuotedPrintable and Base64 are supposedly a much better solution for handling arbitrary Unicode content.

Also, I changes all the example / demo files to use MimePart::Encoding::QuotedPrintable by default.

Thanks!