Saturday, March 10, 2012

E-mail delivery times observed by AuroraWatch UK

Following a comment by one of the AuroraWatch UK followers on Facebook I decided to analyse the AuroraWatch UK email statistics to investigate the variations in delivery times between email providers. It's important to understand that AuroraWatch UK doesn't make predictions but sends out alerts when geomagnetic activity exceeds preset levels. Prompt email delivery is therefore essential for AuroraWatch UK and its email subscribers.

The table below lists the top 30 email domains by number of AuroraWatch UK subscribers. For each domain the worst-case delivery time observed is given.

DomainNumber of subscribersWorst-case delivery timeComments
blueyonder.co.uk72500:05:16
mmail.co.uk34100:05:17
lancaster.ac.uk11400:05:18
live.co.uk32500:05:19
o2.co.uk18900:05:20
tesco.net25000:07:48
btconnect.com14100:07:51
lineone.net18900:07:53
talktalk.net47600:07:54
mac.com22600:07:54
me.com16700:08:45
bigfoot.com10200:09:18
hotmail.co.uk214400:13:15Edit: Similar delays to Yahoo observed in February 2014.
tiscali.co.uk81900:13:26
googlemail.com113800:14:08
gmail.com506400:14:13
ntlworld.com122600:14:16
supanet.com9700:15:25
orange.net11900:15:26
fsmail.net11300:15:28
virgin.net66900:15:33
msn.com35900:15:34
hotmail.com631700:15:53Edit: Similar delays to Yahoo observed in February 2014.
sky.com48200:19:09Uses Google
Edit: as of 2014 uses Yahoo!
aol.com272700:39:47
talk21.com32401:19:12Uses Yahoo!
btopenworld.com49202:44:05Uses Yahoo!
Edit: as of 2014 uses CP cloud, delays much reduced.
btinternet.com387002:48:59Uses Yahoo!
Edit: as of 2014 uses CP cloud, delays much reduced.
yahoo.com131905:29:17
yahoo.co.uk263405:31:11
Total32433

Statistics are based on the AuroraWatch red alert sent 2012-03-09. Failed delivery emails (no such address) are excluded. The worst-case delivery time is computed as the difference between the time of the first delivery attempt and last successful delivery, to reduce the effect of the AuroraWatch UK mail queue. The total number of email addresses on the list was 47486; the first 30 most popular domains cover 69.83% of the subscribers.

Note that it takes a finite amount of time for the AuroraWatch UK email server to work its way through the email lists. It is not meaningful to make comparisons between email providers for worst-case delivery times of less than 20 minutes since the measured performance is highly-dependent on the order the AuroraWatch UK server processed the email addresses. Longer delays are caused by email providers temporarily rejecting legitimate emails for defence against spam. Yahoo's performance is hit particularly badly by their choice to employ this practice.

The original spreadsheet is available on Google documents.