Email problems

[[GSV]Trig]

Not sure if this is the best place for this or not, no doubt it'll be moved if its in the wrong place..

Why is it when emails are sent to the same person from several people within the company, some get through some dont.

email address were sending too is a yahoo.com.cn address.
Some days the Chinese person wont get any emails from us at all.
Some days they'll get them from user A but not B and some from user C but not all.
Then the next day A wont get through, but B and C will..
All emails from here go through the same mail servers but for some reason they dont all get through all of the time.

Damned annoying.

Conspiracy theory is that the Chinese are filtering emails with keywords in them hence some get through and some dont...

[nichomach]

Are you getting any non-delivery reports from the emails that don't get through, or are they just vanishing into the ether without a bounce message?

[Splash]

Are you getting any non-delivery reports from the emails that don't get through, or are they just vanishing into the ether without a bounce message?

This. Also are your mailservers showing the messages as being relayed to the Yahoo mailserver?

[[GSV]Trig]

We get mail reports after about 8/9 days.
Thing is the person were sending to refuses to believe its a problem at there end yet we talk to someone else in China, same problem, guess what, yahoo.com.cn....

Have finally managed to get a form from admins over at yahoo, gonna have to wait for a report to come back tho so I can see where the problem is..

[Jay]

have a look at your mail logs to see if their server is not allowing connections, If so it will show an error code. Do you use a smart host?

Possible causes are

Blacklisted IP address / domain name (I doubt it will be this though)
Crappy spam filter or dodgy cluster config on their end on their end
Overloaded servers (either side)
Maybe yahoo randomly verifies sender authenticity in different ways and at times does not like your mail platform.

[nichomach]

We get mail reports after about 8/9 days.

If you could get hold of one, we could see whether it's a "timed out" type error or the Great Firewall of China telling you to naff off - you know, sort of "SMTP error 5.5.4 - Host GFOC.yahoo.com.cn said: Your message could not be delivered because: We still haven't forgiven you for the Opium Wars. Prepare for deluge of gay porn spam - may you live in interesting inboxes..." or something similar