Confusing and misdirected error message

Our president attempted to send an email, and members (including me) are receiving the following:

Subject: [FreeToastHost] Message Not Delivered: ....... Your message to (This email address is being protected from spambots. You need JavaScript enabled to view it. in This email address is being protected from spambots. You need JavaScript enabled to view it.) had the following error and was not delivered (2 retries):
         [] Failures=[] Recipients=[]
NOTE:  This may be due to an invalid recipient address or high email volume at this time--try again later.
Since I didn't send the message, why am I getting the error?

I also received several empty messages from server@toastmastersclubs.org.

Our club doesn't have a custom domain, we are 789067.toastmastersclubs.org .  

I do see 2 emails to you that had system warnings, they both hadSubject:[Club Photo & Bring-a-Friend Meeting – This Tuesday (11 November 2025)

did you receive the actual emails?

Not really.  In the email mentioned above, there is an attached .txt file, email_176274871493612.txt, with content of the intended email (from club-president, to members-789067@toastmastersclubs.org), 

Following that I receive 4 more emails, (I'll attach one here for information)   

My two clubs are getting the same when sending to the members and prospects email addresses. Seems to have started over the weekend.

I have just done a test, and it's erroring on emails with emojis in the subject line. Emojis in the email body are OK.

tallandbald wrote:

I have just done a test, and it's erroring on emails with emojis in the subject line. Emojis in the email body are OK.
 

Perhaps it's any characters that require special encoding: Subject: =?UTF-8?Q?Club_Photo_=26_Bring=2Da=2DFriend_Meeting_=E2=80=93_This_Tuesday?=
    =?UTF-8?Q?_=2811_November_2025=29?=
Using AI I get the following explanation: 
The subject is split into two encoded parts:
=?UTF-8?Q?Club_Photo_=26_Bring=2Da=2DFriend_Meeting_=E2=80=93_This_Tuesday?=
=26 decodes to & (ampersand).
=2D decodes to - (hyphen).
=E2=80=93 decodes to – (en dash).
Decoded: Club Photo & Bring-a-Friend Meeting – This Tuesday

=?UTF-8?Q?_=2811_November_2025=29?=
=28 decodes to ( (left parenthesis).
=29 decodes to ) (right parenthesis).
Decoded: (11 November 2025)


The space before = in the second part is a common way to handle line breaks in encoded headers and is ignored in decoding.
Combining both parts gives the full subject line as shown above.