remove qmail (dead link, unmaintained)

- it was also removed from debian in 2020 https://tracker.debian.org/news/1147499/removed-106-62-from-unstable/
- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2266

README.md

@@ -416,7 +416,6 @@ Simple deployment of [E-mail](https://en.wikipedia.org/wiki/Email) servers, e.g.
 - [MailHog](https://github.com/mailhog/MailHog) - Small Golang executable which runs an SMTP MTA gateway that accepts all mail and displays in web interface. Useful for debugging or development. `MIT` `Go`
 - [OpenSMTPD](https://opensmtpd.org/) - Secure SMTP server implementation from the OpenBSD project. ([Source Code](https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/smtpd/)) `ISC` `C`
 - [Postfix](http://www.postfix.org/) - Fast, easy to administer, and secure Sendmail replacement. `IPL-1.0` `C`
-- [Qmail](https://cr.yp.to/qmail.html) - Secure Sendmail replacement. ([Source Code](https://sources.debian.net/src/netqmail/1.06-5/)) `CC0-1.0` `C`
 - [Sendmail](https://www.proofpoint.com/us/products/email-protection/open-source-email-solution) - Message transfer agent (MTA). `Sendmail` `C`
 - [Slimta](https://www.slimta.org) - Mail Transfer Library built on Python. ([Source Code](https://github.com/slimta/python-slimta)) `MIT` `Python`
 - [vSMTP](https://viridit.com/vsmtp-mail-transfer-agent/) - Next-gen MTA. Secured, Faster and Greener. ([Source Code](https://github.com/viridIT/vSMTP)) `GPL-3.0` `Rust`