In my case I was doing tests with "contraseña" which is (spanish for password) and it failed

On June 14, 2018 8:36:30 AM GMT+02:00, Tal Einat <report@bugs.python.org> wrote:
>
>Tal Einat <taleinat@gmail.com> added the comment:
>
>It would be extremely helpful to have some test cases that actually
>work for users but fail with smtplib.  So far we have no actual
>examples, likely due to these being passwords.
>
>> Note: it is definitely the case, regardless of what the RFC says,
>that binary passwords need to be supported.
>
>I'm not sure what you mean by "binary".  Do you mean 8-bit characters,
>a.k.a. bytes?
>
>> utf-8 should probably be used as the default encoding for string
>passwords, rather than ascii.
>
>It is also possible that the appropriate encoding here is "latin1"
>a.k.a. ISO-8859-1 encoding.  This specifically includes many
>specialized versions of latin characters, e.g. those with German
>umlauts as mentioned in the duplicate issue #33741.  And it could even
>be the very common Windows-1252 encoding: "It is probably the most-used
>8-bit character encoding in the world." (Wikipedia)
>
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