Overview
Consider an organization which as a high number of users. In this organization, a small minority (usually the top management) need all the collaboration features offered by O365 whereas the rest of the users mainly use only email. In such an organization, there is a requirement to host the email infrastructure of a company across 2 different solutions, such that both the solutions share the same SMTP address space and the company can divide their mailboxes across the two solutions.
For example, in an organization with 1000 users, a typical co-existence between Mithi SkyConnect and Microsoft Office 365 will allow the organization to host 100 users on O365 and 900 on Mithi SkyConnect, sharing a common domain name in their email ids, and with seamless mail flow between the users of both systems.
Mail flow and the checks at different points of contacts
The diagram below shows the mail flow and the point of contacts for a co-existence setup between SkyConnect and O365.
Checks to be done at the different points of contact
Refer to the table below for the recommended checks to be done at the different points of contact depicted in the image above.
| Point Of Contact | Scope | Quarantine Report | |
|---|---|---|---|
| O365 | O1 | As per O365 policies. Incoming Mail is assumed clean | NA |
| O2 | As per O365 policies. Scan for Virus at the minimum | NA | |
| O3 | No checks done. Clean mail expected | NA | |
| O4 | No checks done. Clean mail expected | NA | |
| SkyConnect | S0 | Spam, Virus, Malware for all users Note: The MX can point to O365, in which case the spam, virus, malware protection for all users is provided the O365 system. | Yes (if MX points to SkyConnect. If MX points to O365, refer to the O365 documentation) |
| S1 | Virus check (optional) | NA | |
| S2 | DDOS, Rate control, Auth, Spoof, Virus | NA | |
| S3 | No checks done. Clean mail expected | NA | |
| S4 | No checks done. Clean mail expected | NA |
Mail flow
The table below explains the mail flow between SkyConnect and O365 through the point of contacts shown in the image above.
| Source | Target | Flow |
|---|---|---|
| External email id | SkyConnect user | S0=>LD (Local Delivery) |
| External email id | O365 user | S0=>S4=>O1=>LD |
| SkyConnect user | SkyConnect user | S2=>LD |
| SkyConnect user | O365 user | S2=>S4=>O1=>LD |
| SkyConnect user | External email id | S2=>S3=>ED (External delivery) |
| O365 | SkyConnect user | O2=>O3=>S1=>LD |
| O365 | O365 user | O2=>LD |
| O365 | External email id | O2=>O4=>ED |