We have Exchange 2010 and are using Outlook 2010 as a client. Once in a while, when someone here sends an email to multiple recipients the email is not received. I believe it is only happening when sending to multiple recipients, but I am not 100% sure that it has not occured with just a single recipient.
I just had an example of this yesterday and today. A user sent an email to 4 recipients at 4:05pm yesterday and none of them received it. The same user sent the same email to the 4 same recipients this morning and all of them received it. I checked with the recipients and yesterday's email was not in their junk or trash folders and they didn't make any changes on their end. 2 are gmail accounts and 2 are other private email accounts.
On our end, the exchange server logs show that it passed the emails onto our GWAVA smtp scanner (GWAVA is an smtp scanner that resides on a linux box and scans our outgoing and incoming email). I talked to GWAVA support today and they helped me look through the GWAVA smtp logs and it all indicates that nothing was blocked and that it successfully sent the emails out of our system.
Any ideas as to why it appears that 3 different domains did not receive an email yesterday afternoon but received them today? I also checked to make sure we are not blacklisted and we are not on any lists that I can find.