I use SimpleLogin because the developer gifted me with a lifetime premium account because I helped him telling him he should drop proprietary dependencies and stuff that would help the service be more good for privacy users. but the GUI is prettier still

SimpleLogin is cheaper and has a better interface IMO, though both are very good.

Note that with AnonAddy if you don’t have a proper DMARC setup you will not be able to send emails from your aliases, while SimpleLogin allows it.

Both have a good privacy policy.

AnonAddy has set all the security features. Furthermore, their server mail server also utilises Opportunistic DANE TLS, STARTTLS, PFS, DNSSEC, MTA-STS, TLS-RPT, DMARC, SPF and DKIM.

You can check these information here

SimpleLogin lacks modern ipv6, a proper implementation of HTTPS, (doesn’t mean it uses http) content security policy and referer policy existence.

You can check these information here

I’d would use anonaddy.

SimpleLogin has fancier addresses, plus you can send from these

I’ve used 33mail.com for several years. Works perfectly.