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Thunderbird thinks my email messages are spam

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  • Last reply by Tonnes

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I am having trouble sending emails with Thunderbird, it keeps thinking my emails are spam. What's even worse is once it happens, it then locks me out from sending any emails through Thunderbird. I can send through other platforms if I log in through my phone or webserver. It does not affect my ability to receive emails though.

After a while (hours later), I can then send emails again until it deems another email "spam" and locks me out.

Thanks for any insight!

I am having trouble sending emails with Thunderbird, it keeps thinking my emails are spam. What's even worse is once it happens, it then locks me out from sending any emails through Thunderbird. I can send through other platforms if I log in through my phone or webserver. It does not affect my ability to receive emails though. After a while (hours later), I can then send emails again until it deems another email "spam" and locks me out. Thanks for any insight!

Chosen solution

Thunderbird does a lot of thinking, but it does not classify sender email as spam. What error do you see? Does your email return with a message?

Your IP could be blocked by the SMTP server (or the receiving server) for spamming reasons, for instance because your system was infected previously or still is, or you have a dynamic IP that was used by someone else sending spam, perhaps without the previous user being aware of it. Making sure your system is clean of any malware infections would do no harm.

Your phone uses the telephone’s network, and the webmail does not use the same blacklist check or allows your message to be sent from a different IP, so that does not mean it’s Thunderbird’s fault.

Do you have another email client set up to use the same SMTP settings that is capable of sending mail? Or perhaps your phone is capable of using those settings when connected to your LAN, if any? That way you can find out if the issue is IP related. You could also try to send a message using a different SMTP server to see what happens.

If you have a dynamic IP and are able to refresh (change) it, try opening a command prompt and follow the instructions found e.g. here, make sure it actually got changed, and then retry. Therefor you need to check your existing IP beforehand (by simpy entering ipconfig only), and in case changing it works, to notify your email provider.

Do note that the latter is based on a direct or at least transparent internet connection - on a LAN, you would only refresh your local IP. You might need to perform the refresh from your modem’s interface, or you could disconnect it for a short period in order to achieve the same. If you know your external IP, run a blacklist check such as this one (which will auto-detect it).

Finally and when reading back: if the issue only occurs after successfully sending a few messages, there may be some limitation at the ISP / email provider involved. Try to find out if that is true, or change the SMTP server nevertheless.

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Thunderbird does a lot of thinking, but it does not classify sender email as spam. What error do you see? Does your email return with a message?

Your IP could be blocked by the SMTP server (or the receiving server) for spamming reasons, for instance because your system was infected previously or still is, or you have a dynamic IP that was used by someone else sending spam, perhaps without the previous user being aware of it. Making sure your system is clean of any malware infections would do no harm.

Your phone uses the telephone’s network, and the webmail does not use the same blacklist check or allows your message to be sent from a different IP, so that does not mean it’s Thunderbird’s fault.

Do you have another email client set up to use the same SMTP settings that is capable of sending mail? Or perhaps your phone is capable of using those settings when connected to your LAN, if any? That way you can find out if the issue is IP related. You could also try to send a message using a different SMTP server to see what happens.

If you have a dynamic IP and are able to refresh (change) it, try opening a command prompt and follow the instructions found e.g. here, make sure it actually got changed, and then retry. Therefor you need to check your existing IP beforehand (by simpy entering ipconfig only), and in case changing it works, to notify your email provider.

Do note that the latter is based on a direct or at least transparent internet connection - on a LAN, you would only refresh your local IP. You might need to perform the refresh from your modem’s interface, or you could disconnect it for a short period in order to achieve the same. If you know your external IP, run a blacklist check such as this one (which will auto-detect it).

Finally and when reading back: if the issue only occurs after successfully sending a few messages, there may be some limitation at the ISP / email provider involved. Try to find out if that is true, or change the SMTP server nevertheless.