Single email to guests@ has been sent out 10x now! It won't stop sending it out!

Due to the multiple emails, we just received an email from Bakyt in the World Voices Toastmasters club (completely unrelated to our club) who said his club who also uses FTH and had the same issue yesterday that "recipients received many duplicate emails even though I sent the message only once."

I told him to post his experience here.

Will you up upload that exact file to this thread please.

The attachment can be downloaded here:  drive.google.com/file/d/1LiiK1qnpW695b9Y...Sx5/view?usp=sharing

Hello,I am from World Voices Toastmasters Club. Yesterday, I sent one email to our prospects group after two failed attempts. The third attempt appeared to send only , recipients on the prospects list have received more than 20 duplicate emails within about six hours, and the issue appears to be : prospects-643436@, mail loop, or repeated delivery connected to this email?Thank you,
Bakyt Beshimov
Club #643436
World Voices Toastmasters Club

We are investigating the issue.
Did your email to your gusests have any attachments or or ther lists of cc sent on same email?

Yes, the email included one attachment — a blank Toastmasters membership application , I tried sending the email to both mailing lists together:

• prospects-643436@
• members-643436@

The first attempt used both lists in the “To” field, and the second attempt used both lists in “CC,” but both attempts appeared to fail to , I sent separate emails to each group individually, and those appeared to send , I later noticed that only the prospects group seems to be repeatedly receiving the same email. The members group does not appear to be affected. Some prospects reported receiving more than 20 duplicate emails.