We recommend either gmail or Google GSuite Business Class email. You don't need to pay for a GSuite account as you can send and receive email from a gmail account. Add your siteground or other email accounts as an "additional account" to send and receive mail as @anydomain.com. Gmail so nicely separates email into tabs (personal, social, updates) and the spam and virus filters are second-to-none. Google's GSuite offers business class email for larger companies. Rackspace does a decent job, but email like malware and phishing that shows up in just about ANY other provider, rarely gets through on Google/Gmail.