Gmail treats "@gmail.com" & "@googlemail.com" as the same user account. Using this method, you can have two inboxes, one for all the important mails & the second for all the trash (pun intended).

By creating an auto deletion filter with the query to:(*@googlemail.com), you can have a spam free inbox.

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Furthermore, Gmail also allows adding dots (.) & plus (+) in the username giving you unlimited addresses, like:
u.s.e.r@gmail.com
user+netflix@gmail.com
us.er+amazon@gmail.com
u.s.e.r@googlemail.com
user+pyramidscheme@googlemail.com
us.er+fidgetspinner@googlemail.com

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I love this feature, when I actually remember to use it.

Right ...
Me too ....