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When I respond to certain messages, I get an error message "unknown host" or "unknown user." Why is this?

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Jwcz
Jwcz
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Since the latest upgrade to 31.0, there are times when I will receive an e-mail, but when I send a reply, I get a response saying the message is undeliverable because of an unknown user, or an unknown host. These are messages, I'm replying to and have already received, so it's not a case of typing in an incorrect address.

This happens using both my computer and phone. Not sure why this is suddenly happening now, and why only with certain addresses. Any suggestions? Thanks.

Since the latest upgrade to 31.0, there are times when I will receive an e-mail, but when I send a reply, I get a response saying the message is undeliverable because of an unknown user, or an unknown host. These are messages, I'm replying to and have already received, so it's not a case of typing in an incorrect address. This happens using both my computer and phone. Not sure why this is suddenly happening now, and why only with certain addresses. Any suggestions? Thanks.

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Matt
Matt
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my guess is they have invalid replyto information in the header. As it is on two devices, one of which can not run Thunderbird it is certainly not a Thunderbird issue.