I do some IT support for a friend’s small business and they use my Dreamhost hosting for their email. All was working fine up until a few weeks ago, when all access via OS X Mail stopped working.
I thought it might be a transient thing and told them to use webmail, and went off on my hols.
Today I went over to see what was wrong, and having worked for a large ISP, I’m shocked to find that Sky Broadband are blocking desktop email for accounts that aren’t their own.
For residential ISPs, some blocking is to be expected. Port 25 is used to send email that requires no login, and in an effort to stop spammers abusing this system, most responsible ISPs block this particular port. But the ports used to send email that require a login are normally left open so that people can still use other email systems.
Sky – for reasons known only to itself – are blocking not only the means to send email using authenticated SMTP, but also seem to be blocking receiving email via IMAP. I have never known an ISP to do this, and I can think of no reason why a responsible ISP would seek to do this. The systems to send email can be abused by spammers, but I can’t think of any nefarious way to read email.
I verified that the block was happening by setting my iPhone up with the correct SSL secured settings. Using my 4G connection, reading and sending email both worked fine. Connecting to the Sky Broadband wifi stopped me reading and sending email.
Searching online, Sky have a FAQ about this. Their “fix” is to setup your Sky Yahoo mail account to spoof the address you are trying to use. Anyone who runs their own email system for business or pleasure should have a problem with this:
- Yahoo Mail has a less than stellar reputation for security
- Yahoo is often used by spammers, so it is very likely that Yahoo’s systems for sending email are going to be blacklisted than your own, if set up correctly
- This breaks anti-spam systems like DKIM and SPF unless you make changes to your domain, which effectively says that people can trust emails as coming from you even if they come from one of the spammiest parts of the Internet
- Using two systems for sending email (office and home) means that your IMAP folders can get out of sync
Anyway, in my opinion, this is draconian in the extreme. Rather than being motivated by security concerns, the fact that Sky are blocking secure and authenticated sending as well as reading email means that it must be an attempt to drive people to use the Sky Yahoo offering – perhaps to drive up advertising impressions?