Not able to send to members-3673@toastmasters.org or officers-3673@t....

Hello.
Emails from my email address michaela@delfinder.com are not delivered to members-3673@toastmasters.org or officers-3673@toastmasters.org. Days after sending I receive a message saying:

This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of
its recipients. This is a permanent error.
The following address failed:
members-3673@toastmastersclubs.org
For the following reason:
multiple delivery attempts failed

Am I blacklisted? Can you help?

Thank you.
Michaela

Your address isn't blacklisted

members-3673@toastmasters.org is not a valid address .
Nor is officers-3673@toastmasters.org The domain portion should be @toastmastersclubs.org
The address you have in your error message seems to be the correct address.
Please confirm which address is failing.

The only issue I can see is some warnings where you have sent emails to an address and included the same address in your CC list

Hi Pam,

Thank you. Oh yes, of course I sent the emails to members-3673@toastmastersclubs.org and officers-3673@toastmastersclubs.org. I just mistyped in my support request.

I did send emails to members-3673@toastmastersclubs.org and added guest email addresses in the cc field, is that an issue? The guests received those emails as did all members. Just lately the emails are not being delivered.

The last email which wasn't delivered is one to officers-3673@toastmastersclubs.org I sent on June 28. The subject is 'updated Timer sheet'.

Thank you so much for your help.

I see no emails from Michaela@delfinder.com on June 28 or 29.
Please check you sent to the correct address in the TO:

Thank you. I checked with my email provider and they are saying it might be an issue that my email was identified as spam by the recipient's server.

Does this part of the bounce message help:

--- The header of the original message is following. ---

Received: from imac-michaela.fritz.box ([68.144.194.90]) by mrelay.perfora.net
(mreueus003 [74.208.5.2]) with ESMTPSA (Nemesis) id 0MDRDX-1m3MZi2GbN-00GtGa;
Mon, 21 Jun 2021 22:01:00 +0200
From: Michaela Enzmann <michaela@delfinder.com>

Thank you for all your help.

You are correct, the data center your mail service is hosted in has spammed FTH on many occasions and is blocked.
I have opened up the IP identified in your post.