final answer - very depends from Real Task and Reasons
What did You mean - use just YouCompany.com domain? for what - receive or send? and for what reason? Correct answer for this question - can allow find correct decision.
Short answer - no ready to use software
Half way - use Your company server in POP3 mode with receiving only headers, it's allow You safe more than 50% of traffic
And final - problem is deeper, not just in mail a problem:
- You computer waist up to 2 min for initialize connection
- than all You programs start share this slow channel with same priority with mail, You can switch off autoupdate, but still forget something. Like many program - has it's own updater or send data to servers or etc
- and than, and last - mail traffic
You can saw some examples here -
The best way (I personally use) - redirect YouCompany.com (I use set of rules for redirection) to X-Gate email and use X-Gate (the same as SpeedMail) with RedPort Optimizer. Fantastic result. One of the best function - work with "Big Mail", it's safe You another xx% of traffic and Optimizer kill all parasite traffic from Your computer for 200% :-)
http://www.globaltelesat.co.uk/satph...ion-Tools.html
Regards, Vlad