• yes
• It should be OK this way. The say_helo() is supposed to find out what authentication protocols are supported by the server, but apparently it fails this time. I just checked and some servers return "AUTH LOGIN PLAIN" and some both "AUTH LOGIN PLAIN" and "AUTH=LOGIN PLAIN" as separate lines. I'll tweak the code to allow both whitespace and equals to separate the "AUTH" from the list.
• No.
• $self->{'supports'} = {map {split /(?:\s+|=)/, $_, 2} split /\n/, $res}; looks safer to me.

According to RFC 1869 - SMTP Service Extensions (RFC1869) there should be a space, the RFC 2821 - Simple Mail Transfer Protocol says the same, but seems someone liked equals better ...

The change will be in an upcoming version of Mail::Sender, for the time being either change the line in the module or set the $myMailObj->{'auth_protocols'}{LOGIN}. It doesn't matter much which. If you would set it for a protocol not supported by the server, the server will just report an error.