The best providers for all those services are different. Your domain registrar is not going to be an expert at managing relationships with e-mail providers on a daily basis, which is what guarantees high deliverability at the good e-mail hosts (does it matter how little space you need if some of your mails end up in spam folders instead of inboxes?). The best e-mail hosts are not domain registrars. The best registrars are not the best DNS hosts; it's a value-add to increase average ticket price during checkout, not their core competency. If you really want it all in one, then you have to be satisfied with mediocrity I think.

If you want excellent security and great service for each of those services, then go to a company where that service is their core competency. Host your DNS with your web host or a company like DNSMadeEasy. Host your mail with Rackspace Mail (formerly MailTrust), where you get a 100% uptime SLA, daily backups and 24/7/365 phone/chat/email support. What registrar you use doesn't matter as much since the service they provide is so fundamentally basic -- updating tiny text records in a database -- there's not much that can go wrong. I use Namecheap because of their history of doing right by customers in the face of legal threats where other registrars turn over information and even domain ownership without a court order.