Allow expanding the message header to display more details

[cketti]

In the message view screen allow expanding the header area to display more information about a message.

Information to display:

• display name and email address of sender
• display names and email addresses of all recipients (To, Cc, and Bcc if present)
• full date (in the user's local time and the original time including time zone name/offset)

This is similar to what Gmail does:

Related:

• #5742

[robsmith11]

I agree that it would be very useful to be able to see the email address without having to go into the raw headers.

[cketti]

See #6393