I have three email accounts, one from gmail and two from owned domains. I use Thunderbird to recieve and send email. For the past week, I have not been able to send email from one of my email accounts. This is the error that I receive:
An error occurred while sending mail. The mail server responded: Unauthorized relay msg rejected. Please check the message recipients and try again.
I have checked my settings, and nothing has changed in the last week. The only "work around" I have is to use send through one of my other email addresses.
Email comes in fine for all three email addresses. And I can send fine with two of them, gmail and one of my owned domains.
Please let me know if Verizon has started to block the sending of some emails and what I might be able to do about it.
Verizon recently started implementing port 25 blocking as a way to combat spammers on their network. If you are using your non-verizon.net address to send via a pop3 client, this may be the cause of your issue.
There is more information available at http://www.verizon.net/port25
If you have any questions about the information found there just say so, and myself or one of the other forum members will do our best to find an answer for you.
Hope this helps!