I plan to start a small web technology company and I want to set up a mailing server and client for my inhouse staff such that there are several restrictions in the manner in which they use their mail accounts. Additionally, they should be able to access the email accounts from anywhere. I have thought of Squirremail for anywhere access and Thunderbird as Frontend. I am basically looking at Open Source solutions. Which mail server should I use for backend - Qmail, Sendmail, etc?
The following are the email policies that I wish to adopt:
1. All employees will be given company email account. like firstname.lastname@example.org. I know that is possible if I install squirrelmail server.
2. All mails sent and received by employees can be tracked and stored. i.e All emails sent and received from any accounts can be tracked by administrator.
3. Total size of mail box should be restricted to a few MBs to avoid misuse or probably a size specified by us. This can be specified in Admin Settings and can be changed for individual users. i.e. setting quota for each mail account.
4. Attachment size should be limited to max 1 MB only. Again, this should be customized and can be set for individual users. Again, setting quota size for each attachment.
5. Employees can use this email id to communicate with outside users. There should be special filtering/keyword search to check on the content of mail as well as on attachment before the mail can be send. This should be configurable to add new tags/keywords (e.g jobs, code, etc). Any email which matches the keywords specified in the blacklist should not be allowed to send. Is this the correct approach?
6. All emails sent with attachment should go to HOLD location and on approval from governance team (me or admin) before they are allowed to be released.
7. Set restrictions on the attachment's extension. i.e. no *.exe, etc should be allowed to be added as an attachment. I know this can be overriden by zipping the exe and attaching a zip. But atleast it will place certain restrictions. Any thoughts on a better solution.
8. Content of all incoming/outgoing email is scanned for viruses and any infected email should be quarantined immediately.
9. Mass mailing shouldn't be allowed. A user can't send mails to a group of more then 5-10 people. i.e max email recipients should be a fixed number.
10. Mail should be configurable as desktop client as well as should be accessible remotely through browser. I think using squirrelmail online interface and using Thunderbird as local desktop client should solve this issue.
11. All above features are configurable or controllable for super users like us.
I look forward to hearing feedback from you.