The usernames for the SMTP servers in the password viewer in my installation of Thunderbird also say Not Specified, so I do not think that is the problem.

I cannot explain why Thunderbird works one minute and not the next for a number of people. It occasionally does that for me, as well. However, in my case all indications are that the problem is with the ISPs. Either their mail servers are down or they are too busy. I suspect the real issue with Thunderbird is lack of patience. It appears to stop trying if it does not immediately connect to a mail server. I have also seen Norton Anti-Virus appear to periodically block Thunderbird. Why? Unfortunately, I don’t know. Given the number of viruses and Trojans circulating today, I do not recommend that anyone shut off their virus software just to receive e-mail.

A range of suggestions have been tried without a cure.

When deleting and re-saving smtp password the following was noted.
Under Tools>Options>Privacy>Passwords- ‘Edit Saved Passwords’ in ‘Password Manager’ the entry under ‘Username’ for ’smtp’ states ‘not specified’ while the correct username for ‘mailbox’ IS listed.

Checking under Tools>Account Settings – ‘Outgoing Server (SMTP)’ the username IS listed.

Could this mean that Thunderbird is correctly identifying the username for the incoming mail but is attempting to send mail through the ISP server without identifying the username, resulting in the message above?

If so, is there a setting in Thunderbird>Tools>Options – Advanced – ‘Config Editor’ in the ‘aboutconfig’ window that is relevant to address this (that is, if it is an issue)?

If this is an issue, what caused Thunderbird to be sending through messages one minute and not the next, during the same session?

(No account changes were made mid session, no Windows updates/changes were made that day or on days either side. As a check, MS Outlook on another computer was able to receive/send email through same email account, so this appears to be a Thunderbird issue. My preference is to continue using Thunderbird if there is a solution)

Thanks for the reply and at least you’ve confirmed my suspicions about the majority of my failures, which I’ll now take up with the ISP tomorrow.

However, the remainder are then just Thunderbird SMTP failures as per most of the posts above. I have done the SSL bit, the “get new mail” before sending, re-checked the addressees and even gone back to an earlier version of Thunderbird, but all to no lasting avail, and hence my dilemma.

This is not a Thunderbird issue.

Anyone can use your e-mail address. There is nothing that will prevent a spammer from using it. However, your e-mail IP address is assigned to your ISPs mail servers. You may be sharing those IP addresses with thousands of other users. Report the problem to your ISP. If they do not fix the problem, find another ISP.

Over the past few weeks the number of failures I have when sending email using Thunderbird has increased to alarming proportions, and it takes on average 10 or 12 attempts to succeed.

On the majority of these I get a Spamhaus.org warning that the reason is that my IP address is listed, and this is confirmed on the occasions I have checked.

I always thought that I had only one IP address, but from these spamhaus messages I have figured out that I have had at least half a dozen or more which now makes me consider that something sinister is going on, and that my email system has in some way been compromised.

Can you make any suggestions?

We have not been able to determine if there is any limit to the number of recipients with Thunderbird. Other e-mail clients we have used limit you to 10 recipients in a message and so do many ISPs. According to this Thunderbird forum thread, it could also be your virus program. It is most likely your ISP’s SMTP server configuration. This would be the reason for not receiving any warnings messages. The limit on the number of recipients is intended to prevent spam.

1. Use Thunderbird’s Mailing Lists.
2. Break up your list into groups of 10 or less.
3. Try it again. It should work. If it doesn’t, check with your ISP.

Not all servers have SSL enabled. Most do not. It is apparently not enabled on your mail server. That means that is is not a Thunderbird issue. If you feel that you need to have encryped e-mail, talk to your ISP or hosting company.

Unfortunately, you have not provided any information that helps to identify the cause of the problem. I can offer two pieces of advice:

1) Re-read everything on this page and try the different techniques that people have reported that fixed the problem.

2) Try setting up an SMTP server connection through Bluehost. I am not sure why you are receiving though Bluehost but sending through Rogers. The outgoing problem is likely with Rogers. The vast majority of ISPs deny that the problem is on their end, even after it is proven beyond any doubt to be their problem.