Citigroup Mail Backbone Structure
{"Image DocumentName": "Citigroup Mail Backbone Structure", "Image ImageDescription": "Internet. Anti-spam. Anti-virus. Archiving. It\u2019s very common, especially in large environments, to have layers of mail servers. The anti-spam boxes are the mail1 thru mail5 hosts in the citigroup.com MX records. The other layers are not visible to the Internet. Each layer has multiple hosts in it, providing redundancy and additional performance, and each layer needs to know how to reach the next layer in the chain, without needing to know how the whole structure is organised. There are some problems with this approach. For example, it\u2019s only at the address re-writing stage that we know whether or not the recipient address is valid. So if it\u2019s invalid we need to generate a bounce message inside, and propogate it back out. This could be fixed by making sure that the anti-spam servers know which addresses are valid, and which ones aren\u2019t, and that\u2019s something that we\u2019re working on. Address re-writing. Exchange Servers.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}