| Half as Smart... Twice as Stubborn...

Comcast Blocks Outbound SMTP Email: Port 25

The mules finally got around to checking into precisely why, without warning, SMTP on port 25 was no longer functional in the middle of the night, which is when ambitious mules are working to pay for new barns and fresh hay.

With a dedicated server or ten, the long-eared ones found it very odd that outgoing email was clustering undelivered in Outlook’s outbox. Not a virus. Not general connection issue. Must be the server farm lifting its tail.

After all, the mules are legitimate users and would not be randomly penalized by Comcast, and certainly not without some sort of notice or warning – right?

Hold time at the server farm. Love that music – twangy, yet soporific.

So many emails in the outbox. Shivering masses of them, huddled together, begging to be delivered from evil. The mules felt a great sadness. Foals and clients must be worried and waiting.

Two hours of billable data center admin and tech support later, the mules were much poorer.

And terrifically concerned.

Loss of outbound email service was not the data center’s fault. Instead, the claim was made that, as part of Comcast’s various peer-to-peer (P2P) and bandwidth limitation movements, Comcast is – sans warning – forcing an accelerating number of cable modem subscribers to use Comcast SMTP for outgoing email.

Per representatives of the server host, Comcast gently makes this hint knowing by turning off outbound client email. The host has had many, many calls on the issue.


Port 110 – incoming – no problem. Want to use port 25? Please report to your local re-education centers.

The mules would have saved themselves time with Google in the quest for a remedy, but the problem was nuanced. Who immediately imagines that Comcast would make a move this disruptive without notice?

If your port 25 fails and you can send – but not receive – your email, here is a useful, step-by-step solution guide – it won’t entirely save you from alleged federal spies, but it is an alternative to using Comcast’s SMTP, their presumed intent.

Nothing very new is readily available on the port 25 issue, but, from the horse’s mouth:

“We are singling out spammers on our network and blocking port 25,” said Mitch Bowling, Comcast’s vice president of operations. “We don’t think it’s the right approach to blanket port 25. The right approach is to seek out people who are spamming our network and others.”

Uh huh. That’s ZDNet way back in June of… 2004? Wha…?

Fine, tell us more, Mitch.

“We have commercial customers that aren’t spammers that we don’t want to impact,” Comcast’s Bowling said.

Earth to Comcast: so call or otherwise inform your clients before you go turning off ports.

Spam has not exactly declined four years later. In fact, quite a lot of spam comes from Comcast, which, if one is locked into their floating-IP system, is not a great way to stay visible to others.

The mules have never knowingly sent a spam message, bulk email, BitTorrent in either direction, or even automated confirmations or out of office replies – which makes their port 25 blockage offensive and suspicious – recycled floating IP assignation is bound to “catch” innocents.

Even if blocking port 25 does contribute to halting spam, it sure as hell doesn’t if the blocked parties are not spammers. Instead, it arouses a complacent public, tired of being spied upon or pushed in directions that make little sense, were not properly communicated, and thus spawn paranoia.

If in-house SMTP is not intended as a better mousetrap for innocents and guilty alike, it may only be a bad way to blanket a real issue. Opening client emails and spying for the federal government is apparently good for business, and stopping spam is laughable as implemented to date.

Hence the paranoia – any “spam” and traffic cure should better fit the symptoms.

If spam’s the word, would not a potentially viable solution based on peer-reviewed sender authentication or emailing “unaware zombies” as to what’s going on under their hood better suffice, a method superior to forcing customers to first independently discover and then typically adopt Comcast’s NSA-friendly SMTP channels?

Nah. Too easy. Either find a post like this one and change to port 587, invent and share other options, or you could always contact Comcast for sage advice and courteous service.

Socialist Media for Humans to Click...

1 Unified eMail Support whinnied... 04/3/2013 at 4:39 pm

We have a lot of residential Comcast customers that have just started reporting connection issues due to Comcast restricting both inbound and outbound communications over the standard SMTP port 25. For Comcast customers that have their own on-premise mail server, they can sign up for our Store and Forward Services which we can then forward their mail to them on an alternate (non-blocked) TCP port.

The South Pasture