5,000+ address blacklist: Does any web e-mail have this capability?



Does any e-mail service allow maintaining a large blacklist (>=5000 addresses/domains)?

Why, for what requirement?

To save e-mail addresses from a “subscription bomb”. Accounts were targeted and signed up for thousands of newsletters, retail catalogs, etc. Inboxes are flooded daily so without a practical solution, years held long term e-mail addresses would have to be given up.

Probably not solutions

  • Microsoft’s e-mail service. It seems (same for O365 or Outlook.com) to be limited to 1000 blocked users and domains regardless of the plan chosen.
  • I already have a scrubbed clean list to be blocked (unique addresses/domains only) as a text file. The list size seems to have tapered, which is why I think it’s solvable, not infinite.
  • Spam tools using Bayesian ratings and/or machine Learning. The attacker simply signed up accounts to receive tons of e-mail. A lot from normal businesses that shouldn’t be flagged.

Possible solutions

  • Just discovered Sieve Scripts. It seems not many e-mail web services support them, and their limits are not well documented for given services.
  • Add-ins/Plugsins. Some exist for web e-mail services and can run server side (so all clients benefit). Surprised to find no simple add-in to do this, at least in the MS add-in store and with brief googling. KuTools seemed to have potential but was actually damaging (another story)

More information

  • Fastmail.com supports sieve scripts but it’s no guarantee, waiting to hear back on detailed limitations

  • Really don’t care to run my own e-mail server, less practical than it seems I would guess

  • Requirement wouldn’t grow beyond 5000. Seems the attack was large but finite