More annoying that companies who don’t believe ‘+’ in an email address is valid, are ones that did until their site got redesigned, leaving you unable to log in and having to explain the problem to people that can only read scripts. I’m looking at you, MBNA.
CustomerService@MBNA.co.uk SMTP error from remote mail server after RCPT TO: <CustomerService@MBNA.co.uk>: host mbna.co.uk.s7a1.psmtp.com [18.104.22.168]: 554 No relaying allowed - psmtp
From: firstname.lastname@example.org Subject: Customer Service Reply Thank you for replying to this email. Any emails sent to this inbox are not responded to. If you have a query about your account please check your account details online.