Thunderbird Community Forum

My business has two domains. I can send email to a Gmail account holder using the primary domain with no issues. But amy emails from what I call the "secondary" domain below are treated as spam. This occurs with two different email addresses using the secondary domain.

Both domains are hosted with Bluehost. Exhaustive research has revealed the following:

• Settings in Thunderbird are exactly the same, e.g. ports, security, SSL/TLS, etc. for each domain.
• There is no subject line or content that could possibly be regarded as spam.
• MXToolbox indicates that the secondary domain is not on any blacklist.
• Extended support via Bluehost reveals that SPF, DKIM, and DMARC records are all correct.
• Email sent to a Gmail account using the CPanel (Roundcube) is not flagged as spam. Only emails sent via Thunderbird are flagged.
• Emails sent to a Gmail account from the secondary domain using my mobile phone, but still on the same network/IP address, are not flagged as spam.
• If I first send an email to one of the secondary domain emails FROM Gmail, then reply to it, the reply is not flagged as spam.

After many hours of head scratching (and later, head banging), I am pretty much at my wit's end with this problem. I'm an electronic engineer but this one is definitely out of my wheelhouse. Any help would most certainly be appreciated!

Thanks in advance, Don

Yesterday, 4 Sept a problem developed with my Thunderbird email, namely, when new messages were received they went directly to trash and not to my inbox, i have not tinkered with any settings, The program is on an ASUS laptop, operating Windows 11 pro.

Advice on how to fix without losing all my mail folders thank You Kenneth E. Smith

My Charter.net mail has suddenly started to come into my inbox and automatically is moved to trash by Thunderbird. I do not have antivirus, i have not changed any settings, it is POP.

1) How do I get the emails Thunderbird marks as spam to be moved to the Spam folder without me doing anything. I have thousands of emails now most marked as spam but I have to go in and move them one by freaking one!

2) Also you freaking filter system doesn't work worth a crap! I have created filters for instance: for any emails that have @cypress.com in the From part of the message to be moved to a folder under my inbox named Cypress. I have run it many times and actually none of the filters I've created work? They are very simple to understand and I am doing them correctly as far as I can tell but they don't work. I have created at least a dozen filters and the only emails moved are ones I moved manually myself.

And this training crap you have I don't know what you think it should take a computer to learn to move something to a folder. It's not like a child that has to be taught how to spell. You tell it if it has this in whichever field you've selected then it should move it. Not have to be taught? Not a bright idea in my opinion. It's why AI isn't very smart at least what they release to general users. Anyway I digress.

If you can help me with the above issues in the above paragraphs 1 & 3 I would greatly appreciate it.

I am using thunderbird client on arch linux. I am trying to filter by adding "Reply-To" as a filter. If i look into the source of the email i am trying to filter (i get like 100s of spam messages and only the Reply To seems to be from the same domain in the end) the Reply-To appears in there.

Any idea how to fix that? The other rules work fine, this one only seems to not work

Hello, In our WordPress website, we have a page dedicated to our contact form. I have it connected to the email I have in Thunderbird so I can receive the forms; however, I keep getting the error of:

Mailer: Other SMTP SMTP Error: data not accepted. SMTP server error: DATA END command failed. Detail: Your message has been rejected because you have been detected sending high likelihood spam.

I saw online that I have to contact Thunderbird to resolve this issue since they are the SMTP provider. Please let me know what I should do.

(Note: I am not a coder so if I need to do any coding, please specify where I have to go and what to click)

Thank you

This post is to inform others that release 153.1.0esr finally fixed this previously unresolved issue with spam filters in unified folder mode for me. Up to 140.14.0esr the problem persisted.

I cannot see any other relevant variables in my setup that would have changed concurrently so I am assuming a now fixed underlying software bug as the cause.

After first pressing "Mark" (K), the shortcut keys for "Mark as Junk" (S) and "Star" (S) are the same. Previously, the shortcut key for "Mark as Junk" was (J). Please make the necessary corrections.

最初に「マークを付ける」（K)を押してから、「迷惑マークを付ける」（S）と「スターを付ける」（S)のショートカットキーが同じです。 以前は迷惑マークのショートカットキーは（J)でした。

修正願います。

Some time ago I went tinto exceptions and put in some unwanted email addys and they were blocked. I am getting unwanted emails tried the same thing, but they are still coming through. Here are some of the emails; contact@news.comoundeesgtream.com contact@news.musteraliteinfo.com

Can you tell me how to block these from showing up in my email account? John @ redacted@outlook.com

I use to be able to mark email as junk by right click then K then J. The junk option is not there any more but spam is. The problem is both add star and as spam are both S, so K - S does not work. Need to change one of them to a different letter.

Since yesterday (27 Apr 2026) any and all mail that comes into Thunderbird gets marked as SPAM. I searched online and found people saying that I could reset the junk training filter, so I did this, but incoming mail was still marked as spam. The next suggestion was to delete the training.dat file. Did that, restarted Thunderbird and incoming messages are still marked as spam. The last suggestion was to turn off adaptive junk mail controls. Didn't want to do that because I assumed that it would let spam through. Nope. Turned it off, restarted Thunderbird and two emails from my work came in and got flagged.

I'm running version 140.10.0esr (64-bit) on Windows 11. I am using IMAP to connect to the mail server but it's not running any spam detection software (like Spamassassin). I know this because it's my server and even if it was, no updates have been preformed since the first of this month and this just started happening yesterday. Combine this with the bug that Thunderbird notifies me of incoming mail, even if it's spam (didn't post about this because there are plenty going back a couple of years), is starting to make me look for an alternative.

All e-mails from Pay pal go into trash. Have marked as Not Junk but this has not helped. Needed e-mail from Pay pal today to pick up a click & collect order but didn't receive any e-mail. Tried to log in to Pay pal on Android phone not desktop PC as I usually do. Kept sending codes to my e-mail address to log in but I received nothing. Wasn't until I had come home and accessed Thunderbird on my PC that I found them all in the Trash. Luckily store gave me my order and I didn't have to go back.

Despite my marking messages several times as NOT spam, Thunderbird keeps on and on RE-marking them as spam. And the mails are coming from one of my own addresses, and they ARE in my address book!!!!!

There seems no way that I can stop the beast from misbehaving.

Bonjour, Pourquoi actuellement tous les messages que j'envoie avec ma messagerie Thunderbird depuis mon compte FREE sont-ils identifiés comme spams par mes destinataires GMAIL ?

Good morning.

A few days ago the "Junk" folders in my Thunderbird accounts, without any action on my part, were suddenly renamed as "Spam" folders.

Anyone know why this happened?

Thanks