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12) Our system has detected that this message is likely unsolicited mail to reduce the amount of spam sent to Gmail, this message has been blocked.

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Hallo

I get postmaster return on mail that I try to send to some adresses, some certainly has gmail, some receivers I´m not sure which mailprogram they use. However, those of my messages, where I´m certain that the receiver don´t use gmail - these mail sent from me works just fine and do reach the receiver - without any problem. I do have a gmail adress registered, however I don´t use this very often. I use Mozilla Thunderbird for 99.99% of all of my mail, both sent by me as well as incoming mail.

Many thank´s for helping me Best regards Richard

Hallo I get postmaster return on mail that I try to send to some adresses, some certainly has gmail, some receivers I´m not sure which mailprogram they use. However, those of my messages, where I´m certain that the receiver don´t use gmail - these mail sent from me works just fine and do reach the receiver - without any problem. I do have a gmail adress registered, however I don´t use this very often. I use Mozilla Thunderbird for 99.99% of all of my mail, both sent by me as well as incoming mail. Many thank´s for helping me Best regards Richard

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I cannot tell from your posting if this is an error message you receive when you try to send or a message that people get when they try to send to you. Either way, this message is from someones mail server. That mail server or the person sending the mail has been blacklisted for sending spam. They need to contact their email provider and have the provider get this worked out. It is not a Thunderbird problem. Thunderbird delivered the message to the providers server and the server rejected it.