How to Hide ip address for sending email

This is not a thread about me trying to send spam mail to people. if it was there are other ways of doing so.

I have an honest dilemma on my hands.

I work for a company that makes international sales quite often.

I have been given the task of finding out a way of sending anonymous email from our offices to potential customers. But our office is in SoCal. i need these emails to be sent to the recipient as if they were coming from Mexico or Canada or some other country. How can I send email from lets say MS Outlook 2003 or even a public email account from Hotmail or Yahoo to specific potential customers that are located all around the globe without the real identity of the sender.

I know there are proxy servers, and programs like Hide My IP or whatever, but they do not work well.

I need to send email as if I were in Mexico, with a trace coming back to some part of Mexico (a specified ip address), and with the ability for the recipient to email me back a response, and that response gets forwarded back to the real email address or ip address. I know its sounds a lot or complicated, but if anyone has a solution to this problem i have, it would mean the world to me. Any and all suggestions are appreciated. Thanks.

You can always create fake user on your domain and make it appear as if it came
from sales.staff@yourdomain.com.

If you really need to hide yourdomain.com, then you're into email spamming techniques
and we will not discuss those here. The necessity of this is extremely questionable.
If your recipient is that sensitive, then someone needs -- help.

I would think that international sales would however, be conducted in the language of
the recipient and having staff that is bilingual is always a great asset ;)

you are asking for information on how to spam which is illegal in some jurisdictions and annoying to most people. I doubt you will receive help here. In addition your pretense is dishonest. If I had the ability, I would flood your company with spam so you couldn't spam anyone else. Spam is a great annoyance.