There are several possible reasons why email might not arrive, but the most common is due to failed email authentication. Letterboxd uses technologies (including Sender Policy Framework, or SPF) to ensure that only we are legitimately able to send email from the letterboxd.com domain. Most large email providers respect SPF headers, and refuse to deliver email that did not originate from our servers. If you have configured an address to forward mail on your behalf (say, from iCloud to Hotmail, or similar), the receiving provider may reject the email since it appears to come from the forwarding party rather than directly from Letterboxd.
We suggest that you try adding robot@letterboxd.com to your email contacts, in order to increase the likelihood that you receive our automated emails. If that doesn’t help and you can’t find anything in spam or junk, our team can try changing the email on your account to an alternate address.