Evolution always asks for password when sending or receiving emails on Linux mint because Evolution uses gnome-keyring files. To resolve, do the following steps:
$ cd /usr/bin <enter>
$ sudo ln -s mate-keyring gnome-keyring <enter>
$ sudo ln -s mate-keyring-daemon gnome-keyring-daemon <enter>
Delete the files in ~/.config/mate/keyrings
Reboot.
Now Evolution will ask for the e-mail password once, but without any dialog to create a new keyring.
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