Clusters · filtering · storage · delivery

What happens to
a message, in order.

Most hosts ask you to take the platform on trust. This is ours, drawn out: every stage a message passes through between the sender and your inbox. The design is the result of many years of building ISP mail platforms that stay up and stay clean.

Full schematic (PDF) → Read it as text

01 / The diagram

The whole thing, on one page.

Click the diagram for the full-size schematic. It is constantly evolving — this is the current shape of the platform.

Schematic of the fluent mail platform: mail arrives at the MX cluster, passes through the anti-virus and anti-spam clusters to the mail storage facility, and is delivered out via the IMAP, POP3, SMTP and web clusters.

Click for the full schematic as a PDF (159 KB). Phones load a smaller image automatically.

02 / The same thing in words

Sender to inbox, stage by stage.

A diagram is no use to a screen reader, and no use on a phone. So here is the same journey written out.

Stage 01

The MX cluster accepts it

Your domain's MX records point at our receiving cluster, so an external sender's server talks to us, never directly to your mailbox or your own server. That separation is what lets us filter before anything reaches you.
Stage 02

The anti-virus cluster scans it

Before a message is queued for anyone, it goes to dedicated scanning machines. Infected mail stops here.
Stage 03

The anti-spam cluster scores it

What survives is scored and handled according to the filtering level set on your account — Low, Medium, High or Extreme. The score is written into the message headers, so you can always see why something was or was not filtered.
Stage 04

It lands in the storage facility

Clean mail is written to shared storage rather than to a particular machine. That is why a server can be taken out of service without your mail going with it.
Stage 05

You collect it, however you like

Separate IMAP, POP3 and web clusters read from that same storage, which is why webmail and your phone always agree. If you run your own mail server instead, the SMTP forwarding feed delivers to it — see the SMTP gateway.

Outbound mail takes the reverse path: your client authenticates to the SMTP cluster, which relays on your behalf. Settings for that are on the email settings page.

03 / Documents

For the technically minded.

Both are PDFs. The wholesale overview is the one to send to a prospective reseller's technical people.

Platform

SchematicMail platform schematicThe diagram above, full sizepdf

Wholesale

OverviewWholesale platform overviewFor resellers — see Resellerspdf