GMX Email to Kindle Blacklisted Error from Amazon

Hotrod_Linc · 03-06-2025, 02:08 AM

The Situation
I have been using Calibre for some time now to generate a daily news collection with the fetch news feature. This feature is fantastic, and I have scheduled it to run daily and email the resulting book to my kindle, however for the program to run Calibre must be running on my host machine (obviously). However, I am traveling now and only have my laptop which is unable to be on 24/7. As such I have created an instance of Calibre running on a cloud hosted server to gather and send my news sources.

The Problem
I have configured the cloud instance of Calibre identically to instance on my laptop, using the export/import feature of Calibre. However, once the news is fetched Calibre emails the file with GMX to my kindle, but the email is blocked by Amazon. Amazon autoreplies to my GMX email the error message below, saying my “ip address is blacklisted”

Spoiler:

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Troubleshooting

I believed that it could be a misconfiguration of the STMP settings in Calibre hosted in the cloud. However, given that GMX is receiving an autoreply from Amazon that would indicate that the email was sent.
I checked my laptops installation of Calibre, verifying that the same GMX credentials and book were used, I successfully sent a book through GMX to Amazon.
Both instances of Calibre return a success message when utilizing the “test email” function in Calibre

Conclusions
Taking that both instances of Calibre are configured the same way with the same credentials, I believe there is difference in the way the cloud instance communicates with GMX, which in turn communicates differently with Amazon’s servers.

If anyone has any idea on how I can get past this issue I would greatly appreciate hearing them.

General Info

The instance of Calibre in the cloud is running in a docker container using the image provided by linuxserver.io
As far as I can tell the server instance of Calibre is the regular desktop instance running in kasm VNC
The docker container is managed by me
Access to the docker container is done via reverse-proxy to a url

kovidgoyal · 03-06-2025, 02:36 AM

There is no difference between cloud and non cloud calibre as far as sending email goes, it's the same code.

Presumably GMX forwards the IP address of the client to amazon and amazon is blocking based on that. Though GMX really shouldnt be doing that. Are you sure that reject mail is generated by amazon and not GMX itself?

Hotrod_Linc · 03-06-2025, 03:01 AM

Quote:

Originally Posted by kovidgoyal

Presumably GMX forwards the IP address of the client to amazon and amazon is blocking based on that. Though GMX really shouldnt be doing that. Are you sure that reject mail is generated by amazon and not GMX itself?

Actually, I did not notice that the email itself was from GMX. The sender is "mailer-daemon@gmx.net".

Here is the full email for reference: (personal email info substituted)

Spoiler:

Thank you for taking a look.

kovidgoyal · 03-06-2025, 04:47 AM

Dont see anything useful there, sorry.

pdurrant · 03-06-2025, 09:36 AM

Quote:

SMTP error from remote server for RCPT TO command, host: inbound-smtp.us-east-1.amazonaws.com (54.164.173.191) reason: 550 5.7.1 IP address blacklisted by recipient

It seems clear enough. Amazon's SMTP server won't accept any email originating from the IP address that the cloud-hosted calibre is sending from.

You'll need to route via another email server. I don't have any advice on which email server could do that, as very few accept email for forwarding because of spam.

Hotrod_Linc · 03-09-2025, 10:35 PM

Thank you both for looking into this.

Doing some further research their appears to be some kind of problem with Digital Ocean (the cloud provider I use for my docker instance) and STMP. While I could not find anything concrete, other users mentioned similar problems trying to STMP to Amazon from that provider.

I resolved my problem by using the free tier of a service called STMP2Go, which acts as a STMP relay for my Calibre instance. It works very well, and I have not had a problem since.

PeterT · 03-09-2025, 10:38 PM

FYI: It's SMTP and NOT STMP.

03-06-2025, 02:08 AM	#1
Hotrod_Linc Junior Member Posts: 6 Karma: 10 Join Date: Nov 2024 Device: Kindle	GMX Email to Kindle Blacklisted Error from Amazon The Situation I have been using Calibre for some time now to generate a daily news collection with the fetch news feature. This feature is fantastic, and I have scheduled it to run daily and email the resulting book to my kindle, however for the program to run Calibre must be running on my host machine (obviously). However, I am traveling now and only have my laptop which is unable to be on 24/7. As such I have created an instance of Calibre running on a cloud hosted server to gather and send my news sources. The Problem I have configured the cloud instance of Calibre identically to instance on my laptop, using the export/import feature of Calibre. However, once the news is fetched Calibre emails the file with GMX to my kindle, but the email is blocked by Amazon. Amazon autoreplies to my GMX email the error message below, saying my “ip address is blacklisted” Spoiler: Exact Error Message “This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address failed: xxxxxxxx_kindle@kindle.com: SMTP error from remote server for RCPT TO command, host: inbound-smtp.us-east-1.amazonaws.com (54.164.173.191) reason: 550 5.7.1 IP address blacklisted by recipient” Troubleshooting I believed that it could be a misconfiguration of the STMP settings in Calibre hosted in the cloud. However, given that GMX is receiving an autoreply from Amazon that would indicate that the email was sent. I checked my laptops installation of Calibre, verifying that the same GMX credentials and book were used, I successfully sent a book through GMX to Amazon. Both instances of Calibre return a success message when utilizing the “test email” function in Calibre Conclusions Taking that both instances of Calibre are configured the same way with the same credentials, I believe there is difference in the way the cloud instance communicates with GMX, which in turn communicates differently with Amazon’s servers. If anyone has any idea on how I can get past this issue I would greatly appreciate hearing them. General Info The instance of Calibre in the cloud is running in a docker container using the image provided by linuxserver.io As far as I can tell the server instance of Calibre is the regular desktop instance running in kasm VNC The docker container is managed by me Access to the docker container is done via reverse-proxy to a url

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03-06-2025, 02:36 AM	#2
kovidgoyal creator of calibre Posts: 45,609 Karma: 28549044 Join Date: Oct 2006 Location: Mumbai, India Device: Various	There is no difference between cloud and non cloud calibre as far as sending email goes, it's the same code. Presumably GMX forwards the IP address of the client to amazon and amazon is blocking based on that. Though GMX really shouldnt be doing that. Are you sure that reject mail is generated by amazon and not GMX itself?

03-06-2025, 04:47 AM	#4
kovidgoyal creator of calibre Posts: 45,609 Karma: 28549044 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Dont see anything useful there, sorry.

03-09-2025, 10:35 PM	#6
Hotrod_Linc Junior Member Posts: 6 Karma: 10 Join Date: Nov 2024 Device: Kindle	Thank you both for looking into this. Doing some further research their appears to be some kind of problem with Digital Ocean (the cloud provider I use for my docker instance) and STMP. While I could not find anything concrete, other users mentioned similar problems trying to STMP to Amazon from that provider. I resolved my problem by using the free tier of a service called STMP2Go, which acts as a STMP relay for my Calibre instance. It works very well, and I have not had a problem since.

03-09-2025, 10:38 PM	#7
PeterT Grand Sorcerer Posts: 13,698 Karma: 79983758 Join Date: Nov 2007 Location: Toronto Device: Libra H2O, Libra Colour	FYI: It's SMTP and NOT STMP.