[mail] allow to specify SMTP's MAIL FROM address to config.sendmails(). Closes #3373620
Also modify testlib.Email so we don't loose this information and may test it.
.. role:: raw-html(raw)
:format: html
RSS driven
----------
RSS is a pretty useful technology that can be widely used on this
site. Any set of data can be presented as RSS. You can then plug in
an RSS reader into that and follow the site activity. For example :
:raw-html:`<p><a class="reference"
href="view?vid=rss&rql=Any+X%2CM+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30"><img
alt="rss" src="data/rss.png"> latest changes</a></p>`