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Macmail switching to MD5 challenge-response

Hi. My mac mail keeps switching its authentication from password to MD5 challenge-response. It seems only to be messing up one of my two email addresses, and it keeps changing from not sending to not receiving, all very arbitrary. I change it back to password, and have tried quitting mail, restarting the computer, and the authentication keeps switching back to MD5 challenge-response. Any ideas? Thanks.

IMAC (RETINA 5K, 27-INCH, LATE 2015)

Posted on Mar 15, 2018 4:11 PM

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Posted on Mar 15, 2018 8:54 PM

Turn off the “automatically scribble on my mail server settings seemingly randomly” option in the mail preferences. Okay, I’m paraphrasing that slightly, but there’s really a checkbox in the server settings that does basically that. Automatically manage connection settings in Mail on your Mac - Apple Support Try disabling that, and see if the settings stick.

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Mar 15, 2018 8:54 PM in response to goldwolf01

Turn off the “automatically scribble on my mail server settings seemingly randomly” option in the mail preferences. Okay, I’m paraphrasing that slightly, but there’s really a checkbox in the server settings that does basically that. Automatically manage connection settings in Mail on your Mac - Apple Support Try disabling that, and see if the settings stick.

Mar 15, 2018 10:14 PM in response to MrHoffman

Thanks! I actually prefer the paraphrase.

This may have done the trick. Of course, right before I made this change, things started behaving again.

I'll see if it still works tomorrow.


Do you have any idea why MD5 challenge-response would be designated? I've seen some old forum posts that say it's more secure...which I guess it is if you can't send or receive emails.


Thanks again.

Mar 16, 2018 7:44 AM in response to goldwolf01

A challenge-response MD5 hash of the password is preferable to authentication involving a cleartext password. Preferably all happening over SSL/TLS link and not over an unencrypted cleartext network link. MD5 is a better choice, if the server supports it. I’d find a replacement for any mail server that even offers unencrypted cleartext network connections much less requires those. Seems there’s either a problem with this mail server and its support for MD5 authentication, or maybe there is something else going on here.

Macmail switching to MD5 challenge-response

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