This can happen for a few reasons, such as trying to send on an smtp with non-secure settings, or including a signature in the message. Who is the mail provider?

https://support.mozilla.org/en-US/questions/1367576

My email provider is iPage. I just tried sending an email to multiple recipients using webmail, and it worked just fine.

Also I don't have a signature in my email. THanks for your continued help with this.

iPage offers secure and non-secure settings. Which ones do you have? The secure ones for the outgoing are smtp.ipage.com on 465, SSL/TLS, normal password, User Name = email address.

https://www.ipage.com/help/article/email-client-setup

How many contacts are you sending to?

It doesn't matter if I send to 2 or 20 - the email just gets stuck in sending. My secure settings was set to None. I changed it to SSL/TLS and it didn't fix the problem. The only other option is STARTTLS.

For smtp:

• Server name: smtp.ipage.com
• Authentication Method: normal password
• User Name = full email address.

• If using Port : 465
• Use Connection Security: SSL/TLS

• If using Port : 587
• Use Connection Security: STARTTLS

After making changes - restart Thunderbird.

Thank you for this help - I'm so grateful. I changed to smtp and that solved it. Still have a few questions: What connection security if I'm using port 993? That's what it's currently set to. Should I change to 465 or 587? And what is the difference between using imap.ipage.com (former setting) and smtp.ipage.com? And any idea why I would have had this problem sending to more than one recipient, all of a sudden? Something I did? Want to avoid in future! THANK YOU

The incoming server imap.ipage.com has SSL/TLS security on port 993, while the outgoing smtp.ipage.com has SSL/TLS security on port 465. Some providers use the same server address for incoming and outgoing, but for iPage they must be distinct. If you had imap.ipage.com for the outgoing, that would produce errors.

Incoming settings: Tools/Account Settings, Server Settings.

Outgoing settings: Tools/Account Settings, Outgoing Server (SMTP).

GOt it! So for the incoming port 993, should I use STARTTLS or SSL/TLS?

SSL/TLS for incoming IMAP on 993.

Many many thanks!

Hello, I have this same problem and none of the above is working for me. As a test, I downloaded another email client and was able to email as many recipients as desired in one outgoing email. Next things to look at?

Also, after years of seamless use, why did this surface a day ago? I changed nothing on my end.....