Handle users expectation about responding to email notifications

[tobifjellner]

Several social networks now have functions that allow users to comment by simply responding via email to notifications they received.

I just had a user in the Swedish support forum comment that she first responded via email, but it didn't work.

It would be good to address this expectation:
Either by actually providing the possibility to comment/respond to topic by replying to an email.

But since that's not too easily done, we could at least try to set more specific expectations.

In the following two functions:
replace_forum_subscription_mail_message()
replace_topic_subscription_mail_message()

We could expand the substring:
"Login and visit the topic to unsubscribe from these emails."
into
"Login and visit the topic to reply to the topic or unsubscribe from these emails. Note that responding to this notification has no effect."

[sterndata]

"Login and visit the topic to reply to the topic or unsubscribe from these emails. Note that replying to this email has no effect."

[Clorith]

Seems like a quick win that makes sense to include, many users these days are unfamiliar with the noreply@ concept, and we never state anywhere that you can't respond directly.

[obenland]

In 7560:

BBP: Make clear that replying to emails won't work.

Props tobifjellner, sterndata.
Fixes #3730.

[noisysocks]

I think this has regressed. Emails from the WordPress.org Forums don't contain anything to indicate that you can't reply to the email which is confusing for users (including myself who just got caught out by this :D) See attached screenshot.

[dd32]

I don't think has regressed as such, it's just that this is an individual topic subscription and not a term/tag/plugin/theme subscription email, and that was never updated.

[dd32]

In 10158:

Support Forum: Add a "you can't reply to this email" note to topic subscription notifications.

Fixes #3730.

[iandunn]

I think it'd also be good to bounce any emails sent to noreply@, since ​people don't read email.