Emails from social networks are marked as spam 100% more often then those from other sectors, and in the case of Friends Reunited, one in four of its emails failed to reach the inbox.
According to Return Path, the deliverability issue is partly a result of spam complaints from recipients, which suggests that social networks need to take a closer look at the issue.
Friends Reunited sends around 30m emails per month, and found that almost 33% were not reaching subscribers' inboxes. While 5.7% ended up in recipients' spam folders, 27% were blocked at ISP level.
Return Path managed to improve this deliverability rate from 67.1% in May to 92.5% in June 2010, but the fact that ISPs are blocking such a high percentage of social network emails suggest that others may need to look at their email strategies.
I suspect the sheer volume of emails from Facebook, Twitter and others is a big part of the problem, and perhaps these sites need to send fewer emails, or bundle news into a daily update.
With emails telling you that someone has commented on your photo, or that you have a new follower, the number of emails soon mounts up, and for people who have become disinterested, its often easier to hit the spam button than the unsubscribe link.
These firms need to make it easy for people to unsubscribe from emails, and also provide options to allow subscribers to adjust their preferences and reduce the frequency of emails.
You can immediately unsubscribe from all Facebook emails, and this process take just two clicks from the email, though you need to login to adjust preferences. This is a good approach though, as it allows you to hold on to subscribers who may otherwise opt out.
Another tactic is to remove inactive subscribers from databases as they are much more likely to hit the spam button, driving down reputation metrics, and affecting the deliverability of the whole database.
Deliverability issues also represent a waste of marketing budgets; Econsultancy's Email Census 2010 found that companies lost an average of 9% of their email budget due to non-delivery of emails.