SMTP connection errors – 8 March

We Our Cape Town infrastructure has been struggling with outgoing spam scanning, resulting in SMTP connection errors.

In an attempt to be a good neighbour to the rest of the Internet, we recently implemented spam scanning of outgoing email. Email relayed through our servers are legitimate, but occasionally a user’s password leaks out (weak password, malware on user’s device?) and spammers then use their login to send junk. Scanning outgoing email helps mitigate damage caused by such spam incidents.

The idea is good, but in practice we are seeing that our servers sometimes have a hard time keeping up with the spam scanning. Some spam checks rely on external services, e.g. matching with trending spam. This causes a few seconds delay in processing every SMTP submission. In some cases, especially from the Cape Town data centre (that has a “slow” connection to these external services), the delay can be significant and cause time-out error. On Friday and again today, we saw such errors with resulting inconvenience to our users.

For the time being (and likely permanent) we have disabled outgoing spam scanning at SMTP time. However, we will continue to scan forwarded email. This is particularly important for messages that forward to Google and Microsoft services. Sometimes our spam filter misses a junk messages and their filter would catch it; we do not want to avoid forwarding spam and getting in trouble with those guys.

We are not disabling spam scanning for incoming messages. We will do our utmost to keep the junk out of your inbox.