There are two duplicate suggestions you can vote for:
Allow “semi-catch-all” emails like “firstname.lastname@example.org”.
(in the “Mail - Addresses” category)
Allow support for “plus”-style email addresses: email@example.com goes to firstname.lastname@example.org.
(miscategorized in the “Mail - Filters and Spam” category)
Please do vote for one or both, I’d like to see this implemented myself.
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