Sent e-mails to invaiid addresses do not get returned?

[Ant]

Hello.

Is it me or do many invalid e-mail address (e.g.,
thisshouldfa...@dslreports.com) do not get returned when sent from
TWC's RR servers (mail.twc.com (port 587 and StartTTLS) and
https://webmail.roadrunner.com? I get repeat these tests and got them
returned. It's weird that RR's email server doesn't.

Thank you in advance. :)
--
Quote of the Week: Captain Marvel: Shazam. Billy Batson: Now put her
down. Black Adam: See? Like an ant. --Superman/Shazam!: The Return of
Black Adam
Note: A fixed width font (Courier, Monospace, etc.) is required to see this signature correctly.
/\___/\ Ant(Dude) @ http://antfarm.ma.cx (Personal Web Site)
/ /\ /\ \ Ant's Quality Foraged Links: http://aqfl.net
| |o o| |
\ _ / Please nuke ANT if replying by e-mail privately. If credit-
( ) ing, then please kindly use Ant nickname and AQFL URL/link.

[Ant]

Jim H <inv...@invalid.invalid> wrote:
> On Fri, 07 Jul 2017 16:48:29 -0500, in
> <sqydnfBNhLwwnP3E...@earthlink.com>, ANT...@zimage.com

> (Ant) wrote:

> >Hello.
> >
> >Is it me or do many invalid e-mail address (e.g.,
> >thisshouldfa...@dslreports.com) do not get returned when sent from
> >TWC's RR servers (mail.twc.com (port 587 and StartTTLS) and
> >https://webmail.roadrunner.com? I get repeat these tests and got them
> >returned. It's weird that RR's email server doesn't.
> >
> >Thank you in advance. :)

> How do you know that mail.twc.com server is the problem. The
> dslreports.com server could be simply swallowing the mail to invalid
> addresses. You might want to test by sending to an invalid domain
> rather than an invalid username.

Then, how come my other e-mail providers (e.g., smtp.earthlink.net) get
returned e-mails with the same invalid addresses I sent to? Both
mail.twc.com and https://webmail.roadrunner.com never returned anything.
:(