regarding ssl certificates

[Jochen Bern]

On 03/15/2019 06:03 AM, Gary wrote:
> Is there some reason to use a mail.domain.com cert for mail rarher than
> just using domain.com for everything? 
> 
> Historically the subdomain were used because they were on different
> hardware. That is www was on one machine and mail was on another.

Actually *THE* original approach was
a) to make ftp.mydom.ain a CNAME to machine4711.mydom.ain or similar,
b) attaching that latter (usually by A and PTR RRs) to the physical
   hardware for its lifetime, and
c) use the naked mydom.ain for e-mail addresses and thus, since MX RRs
   did not yet exist back then, have its A or CNAME RR point to your
   incoming SMTP server.

When it became apparent that using the domain name - typically
representing your organization as a whole - for a specific service
wasn't *that* bright an idea, the e-mail aspect was repaired by the
introduction of MX RRs. During the time that took to get implemented
everywhere, other services still used ftp.*, gopher.*, what have you,
even the early www.* .

Then came the day when Eric Allman decided that the new version of
sendmail shall replace CNAMEs in e-mail addresses, local admin's opinion
on the matter and existing working setups be damned. As far as I can
tell, *that's* what ended the era of the "functional names shall be
CNAMEs" paradigm.

*Today* web designers opine that an organization's website is *so*
important that it merits repeating the old error of putting it under
mydom.ain instead of www.mydom.ain, even if it's hosted someplace that's
not under *your* control in the first place. I'm fighting that wherever
I can (and unlike many of those "professionals", I *do* have the
technology at hand to have something respond to HTTP(S) at mydom.ain and
throw back a HTTP redirect to www.mydom.ain).

Regards,
-- 
Jochen Bern
Systemingenieur

www.binect.de
www.facebook.de/binect

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