Thunderbird itself will never block sending to an email address... but your email provider might. Please quote any error messages (completely and exactly) you see when you try.

Similarly, Thunderbird won't block incoming email, though it might mistakenly classify it as spam. Again, please describe what happens to this incoming email that makes you consider it blocked.

I do notice that the garmin thing you mention above is not a correctly-formed email address, so it couldn't go anywhere.

Dear Lin, Here's more details on my original problem: thunderbird is not sending or receiving email to a particular legitimate email address; never had this problem in the past--it's just one particular email--please stop blocking it; @inreach. garmin.com. Inreach is a system for sending and receiving emails when outside cell phone ranges; hundred thousands of people use it in Alaska and world-wide; I've used it with emails to and from my Thunderbird email for over ten years. To send email to my Thunderbird email wilbur2@alaska.net, I send it from my Garmin Inreach device with sending address: wilbur2@inreach.garmin.com. My son does the same thing, all the time, to my Thunderbird email wilbur2@alaska.net. His address on garmin site is: charliejagow@inreach.garmin.com. After message received the first time at Thunderbird, to reply, there is, in the body of email a Garmin link that one uses to get to Garmin site to send message to the Garmin device. I've already talked to tech specialists at Garmin; the problem is not at Garmin. These Garmin devices are extremely common, and no one I know has had this problem.

Dear Lin: Here is more info on Thunderbird rejecting email sent from my Garmin device several days ago: **********************************************

   **      THIS IS A WARNING MESSAGE ONLY      **
   **  YOU DO NOT NEED TO RESEND YOUR MESSAGE  **
   **********************************************

The original message was received at Wed, 15 Apr 2026 02:40:53 +0000 from 74-124-98-79-radius.dynamic.acsalaska.net [74.124.98.79]

  ----- Transcript of session follows -----

<charliejagow@inreach.garmin.com>... Deferred: Connection timed out with inreach.garmin.com.cdn.cloudflare.net. Warning: message still undelivered after 4 hours Will keep trying until message is 5 days old

Reporting-MTA: dns; mail41c28.carrierzone.com Arrival-Date: Wed, 15 Apr 2026 02:40:53 +0000

Final-Recipient: RFC822; charliejagow@inreach.garmin.com.cdn.cloudflare.net Action: delayed Status: 4.4.1 Remote-MTA: DNS; inreach.garmin.com.cdn.cloudflare.net Last-Attempt-Date: Wed, 15 Apr 2026 07:12:19 +0000 Will-Retry-Until: Mon, 20 Apr 2026 02:40:53 +0000

X-Authenticated-User: wilbur2@alaska.net ARC-Seal: i=1; d=carrierzone.com; s=mailmia; a=rsa-sha256; cv=none; t=1776220854; b=opWnr4EPIqOjqzT5+d7prljExWP3Vjj9ZNjndsRaUYFCa6hlyAzD4L325zCOM+fvXtaT qAWCOxAzIwxeeB47w1xyIRlsIFfsMzkDxrrL9COEwbenfhnrGBU94tzhTQF81tRlwuizU FqBHQrmoFIJTsNFFnK5BSsHP1kS+zrtSsM= ARC-Message-Signature: i=1; d=carrierzone.com; s=mailmia; a=rsa-sha256; c=relaxed/simple; t=1776220854; h=Message-ID:Date:MIME-Version:To:From:Subject:Content-Type; bh=ij/BzjZ/7FJuXj1GOLxNR0qfGEnDQEGOzAAn8GAajtQ=; b=Lv1tenLUQTuHFIgfVxuLFCe1gsvkqINElf7cMB2FpctilyWQuNecUJ0g4xpxBo6kFy07 qp30EuysL4TYFdNypnMrpvoWPiCvlHbUgCRbdZuR2YSMTxYtuoZB7hkiGZzGDHiNP9zic v8bjCoTZ4ftZYH4uUPOCoR4F++Jcd3mo0I= ARC-Authentication-Results: i=1; mail41c28.carrierzone.com; auth=pass smtp.mailfrom=wilbur2@alaska.net; arc=none smtp.remote-ip=74.124.98.79 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alaska.net; s=hmail; t=1776220854; bh=ij/BzjZ/7FJuXj1GOLxNR0qfGEnDQEGOzAAn8GAajtQ=; h=Date:To:From:Subject; b=tt+33Dwx85bM9ws6ywr4k/971slDtwNRJ3j31n8GY8oTt0ehl9VmUVbj7BhO0PJ59 4i9BpQBIKN9mh89EjWO7k1H8w/HKAq96TTOD+nPOj1WmstcEg0V3kZTkZNfFsdjjCt rMpkag00ulr8JT4AK45xt8egZkEo0JdTf87Jg/9NfP1Poj4BVW2rhM1vSub8ggex48 LtYWEZ9b15NZG0cacGEr+gqqKrK30zs9XCNbS3EbeXANCYN9Vjzbh59yU1df5Zj23+ 1f+fwJ81EJlrB3pGGl4l1srmkTqwCqC2HaBhVD4TE3CaLMaS6ILCPsoSbCn0NNkPVc iKIHx1Hji/v9A== Feedback-ID:wilbur2@alaska. Authentication-Results: mail41c28.carrierzone.com; auth=pass smtp.mailfrom=wilbur2@alaska.net X-Envelope-From: wilbur2@alaska.net Return-Path: <wilbur2@alaska.net> Received: from [192.168.1.146] (74-124-98-79-radius.dynamic.acsalaska.net [74.124.98.79]) (authenticated bits=0) by mail41c28.carrierzone.com (8.14.9/8.13.1) with ESMTP id 63F2eoOc1795336 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO) for <charliejagow@inreach.garmin.com>; Wed, 15 Apr 2026 02:40:53 +0000 Message-ID: <c9d606a0-f9fd-4ab6-91dc-28d78cb201c1@alaska.net> Date: Tue, 14 Apr 2026 18:40:50 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: charliejagow@inreach.garmin.com.cdn.cloudflare.net Content-Language: en-US From: Paul Jagow <wilbur2@alaska.net> Subject: wx Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-VADE-SPAMSTATE: clean X-VADE-SPAMSCORE: 0 X-Rspamd-Status: No, score=-0.10 X-Rspamd-Result: default: False [-0.10 / 6.00]; MIME_GOOD(-0.10)[text/plain]; RCVD_COUNT_ZERO(0.00)[0]; FROM_HAS_DN(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:7782,asn_org:"Alaska Communications Systems Group, Inc.",country:US]; RCPT_COUNT_ONE(0.00)[1]; MID_RHS_MATCH_FROM(0.00)[]; TO_DN_NONE(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; LOCAL_OUTBOUND(0.00)[]; VADE_SPAMSTATE(0.00)[clean] X-VADE-SPAMCAUSE: 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 X-Origin-Country: US

This is a server error message, NOT a Thunderbird message. It appears to me that the message is currently held on acsalaska.net's server. It seems to be having trouble delivering it to domain inreach.garmin.com.cdn.cloudflare.net . The message you received says that they will keep trying to deliver it for 5 days before they give up.

The email header analyzer I used mentions that the message failed Sender Policy Framework (SPF) Authentication, which is a security protocol servers use to approve communication between them. I don't know that that's always accurate, and I believe that the failure is not always fatal - it depends on how the servers are set up - but that might account for your message delay. It's a mail server problem and there's nothing you can do about it on your end unless you can reach a tech support person who can control the server or knows who can.

This is pushing my knowledge of how email systems work, but I believe Thunderbird did its work successfully and the message is currently stuck in server limbo.

Dear Lin: Yes, the problem was the email provider, not Thunderbird. Acsalaska tech support fixed the problem--the messages weren't in the regular spam, but in spam on Alaskacom's webmail. Problem solved, thank you for your help