A few minutes ago I tried to log in to Thunderbird again, and again it said the password was incorrect and I had to enter it again. But instead, I went to the Comcast website and logged in with my new password, and looked at my email there. No problem!

So what's wrong with Thunderbird????

Remember, I initially logged in, it asked for my new password, I entered it, and all was fine. But it then wanted the password AGAIN when I attempted to send an email. So I entered it in again, and was able to send an email. Now it wants that new password again. How many times does one have to enter a new password???

Once and you edit the saved one. If you enter password but do not select to remember password then it does not get remembered.

However, That mesasge "An error occurred while sending mail. The mail server responded: Polite people say HELO first. Please verify that your email address is correct in your account settings and try again." is very odd because it's too personal and I would be suspicious. If you have changed a password then someone maybe trying to get hold of it again.

The first thing to do is get your computer checked for virus malware etc. Exit Thunderbird. Exit all programs. Restart The computer in 'Safe Mode' Run Antivirus Malware full scans. You may have someone who has access to your computer. You may have keylogging software being used by nefarious person. Safe Mode means not using internet so it's running basic OS software.

Only when you are certain computer is clean do you restart computer and immediately change email passwords.

Another piece of evidence in that Constant Contact (CC) list problem.

I was on the phone with CC and they said that in the past 3 months or so I was unsubscribed a total of 5 times! At no time did I unsubscribe. The agent then put me back on the list and sent me an email. Within about 3 seconds I was unsubscribed again! Their history data showed the same thing - I was always unsubscribed within a few seconds of being added.

No human could be that fast consistently. Therefore, some automated tool is doing this.

So, does Thunderbird take it upon themselves to do email filtering? I do have blacklist and whitelist filters set up, and I monitor them regularly, as well as my junk/trash filters. But CC doesn't show up anywhere.

The other alternative is that my Comcast ISP is doing the automatic rejections.

Any ideas here?

re :Constant Contact (CC)

Suggest you check that you are not contravening any of their rules, just in case something is triggering an 'unsubscribe' - btw - impossible to do this in Thunderbird unless you get an email and you click on an 'unsubscribe' option.

• https://knowledgebase.constantcontact.com/email-digital-marketing/articles/KnowledgeBase/5305-constant-contact-s-email-permission-policy?lang=en_US

I did find this info on the CC forum which may apply to you - worth checking:

• https://community.constantcontact.com/t5/Questions-Discussions/Constant-Contact-keeps-unsubscribing-new-customers/m-p/409550

example: The most common reason for that is when you forward an eblast to someone. When they are finished reading it, they click “Unsubscribe”; at the bottom of the eBlast. However, CC Unsubscribes YOU, not them! You can prevent that by deleting your email address at the bottom of every eBlast before you forward the eBlast.

• https://community.constantcontact.com/t5/Questions-Discussions/User-Being-Unsubscribed-Unwillingly/m-p/409334/highlight/true

re: does Thunderbird take it upon themselves to do email filtering? IF you have manually created a filter in 'Message Filters' - (usually used to auto move new incoming mail into a suitably named folder) then this sort of simple filtering is possible.

IF you have enabled the Junk Controls and trained the junk filter to recognise what you consider as junk/spam then you can set up that mail account to put those emails in the accounts Junk/Spam folder. But you will still have access to them.

IF the server itself marks emails as spam and you are using an IMAP mail account then those emails will display in the Spam folder. However, if you using a POP mail account which can only access server Inbox then any email your webmail account puts into server Spam folder will not get downloaded to the Pop account. You would only see those emails if you logged on to your webmail account.

Thunderbird is just a program running on your computer. There is no server - no server filtering etc.

re : I do have blacklist and whitelist filters set up,.....But CC doesn't show up anywhere.

In Thunderbird, the 'whitelist' is set up in Junk Controls and basically means any email address set up as a contact in an a selected address book is considered in a whitelist.

The Junk Filter Log (providing it's switched on) will tell you what your own Message Filters are doing with any email that gets filtered. So you can double check to see if one of those filters is somehow picking up something in a CC email which performs whatever you set it to do. The Filter Log button is in 'Message Filters' window bottom right.

re :The other alternative is that my Comcast ISP is doing the automatic rejections.

That is a very real possibility.

Your mail account in Thunderbird can only download from server Inbox, if Pop OR display whatever is on server if imap.

First you need to be certain your comcast mail account is actually receiving those emails. Logon to Comcast webmail account via a browser, then get emails sent from CC and wait to see if they turn up in the comcast webmail account and if yes note the folder they are being put into. If they are not being received onto server then you are never going to see them in Thunderbird. Comcast and indeed any server will have it's own Spam filters. There are occasions when email is marked a spam but still is shwon in mail account. However, if the server has decided too much spam from a certain IP address or email address is being sent then it could just block the emails and they disappear in the void of space.

Spamhaus is a decent starting point to check for that issue. https://check.spamhaus.org/