Perhaps you might like to share the connection setting your are using? including the mail provider as some do not use the default ports for submission. Some are still in the last century using 25.

Knowing what the error message you receive is vebatim, would help in moving to facts from guess work.

Outgoing server # 587 this is what Spectrum gave me. Here's the complete error message:Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.charter.net was lost in the middle of the transaction. Try again.

smtp.charter.net is my outgoing server

Kristi

I was very confused by your first post. Now I start to understand. However it sounds like you got very little if anything from the spectrum support person other than what is ostensibly the default port to send mail via SMTP.

Connections being lost in the middle of a transaction can have many many causes. From incorrect settings to antivirus programs getting in the way.

So to begin you need to check your outgoing server (SMTP) entry in the account setting is configured using the settings Specrum use. These appear to be

Spectrum Server mobile.charter.net port 587 security TLS username Your full email address Authentication Method Normal password

Do your setting match those?

Are you connected to the internet using spectrums service? Historically they only allowed you to send mail if you connected to the internet from their service, so hotspots while on holiday would get mail, but not send it.

Matt, thanks for your patience. Pretty sure server is mobile.charter.net. First time port 587 has been pointed out to me. Also have no idea what security TLS means or how to confirm that. Username is correct. Authentication Method is also new to me but I do have a password. Yes, Spectrum is my internet provider. Not a holiday, haven't had this issue in years.

As I said before go to the outgoing server (SMTP in account settings) that is going to be essential to check what is set and also to make any changed.

So right click on an account in the folder pane, select settings from the menu. Scroll in the account setting dialog that opens until you see outgoing server (SMTP) in the list an click on it. Now compare the information in there with what you have from this topic. Do they match.

<last minute observation> I might be late with this little amendment, but in Thunderbird TLS shows up as connection security. Not security. I was copying from the web for that stuff and missed that difference. </last minute observation>

BTW you don't have to understand what the settings are, or what the terms mean, just be able to copy what is required by the mail provider.

PS. TLS stands for Transport Layer Security. (and your none the wiser, and really neither am I.) I just know it is encryption on the connection to the server. It is immensely complex under the hood and heavy on the mathematics (it is cryptography after all) but it just works for you and me. So it is also simple. A couple of explanatory links if you are interested https://www.cloudflare.com/learning/ssl/transport-layer-security-tls/ https://en.wikipedia.org/wiki/Transport_Layer_Security

I did so. smtp.charter.net & 587 is outgoing server #. I've also powered off, unplugged everything, three different times. No change. Still cannot send emails.

Hello  ? Anybody out there to help me with my emails ? Can receive, cannot send. Had a chat going on with Matt which resolved nothing. Problem started last weekend.