summary request for email issues

Mike Starke wrote:

> Would someone be so kind as to post a short, concise
> 'Howto' "fix" their smtp issues for each MTA? I could
> do Qmail, but it would end there. I think we need
> a summary for those who may search the archives
> on a later date.
>
> Qmail, Postfix, Exim, Sendmail, (any others?)

Archives from last week or so should have each of those in it already.