suggestions for better "add e-mail account" icons.

mailbox_1_slim_plus_on_right_side.svg

mailbox_2_slim_plus_in_the_bottom_right_corner.svg

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mailbox_3_filled_plus_in_the_bottom_right_corner.svg

mailbox_4_filled_without_plus.svg

mailbox_5_slim_without_plus.svg

mailbox_6_slim_with_plus_in_the_bottom_right_corner.svg