Only show SMTP envelope recipient when relevant

[c960657]

Motivation

The SMTP envelope recipient usually reflects the To, Cc and Bcc email headers. The mailer preview only shows SMTP the envelope recipient (SMTP-To) if it differs from To, but it does not take Cc and Bcc into account.

Screenshot:

Detail

This Pull Request extends the check for SMTP-To to cover also Cc and Bcc, so it is only displayed in the rare event that the envelope recipient has been manually overriden.

Also, show the list of email addresses without array brackets and quotes.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[c960657]

Thank you for your review and improvements.

[jonathanhefner]

I pushed a commit to squash the commits.

Thank you, @c960657! ✉️