I've had this problem for a long time now and yet to find a solution.

When I send mail (using Apple Mail on OSX 10.7.5), in particular to larger corporates with mail filtering systems, it will always reach its destination but sometimes when the recipient replies, my actual reply address is stripped and it replaced by a combination of my name and the mail server domain name. Unusually, it will often get to me, but to the sender, it looks like they have sent to another address and doesn't look very professional.

I'll try to give an example.

- my email address is peter@mydomain.ie
- my reply address should be peter@mydomain.ie
- I send an email to a work contact. They reply to my email
- I receive their email but it looks like they sent it to peter@mxfilter.serverxyz.com
- Another symptom is that, depending on the mail client they are using, the 'from' field appears empty in their inbox.

Things I've tried (unsuccessfully)...

- Changed from Thunderbird mail to Apple Mail, same problem
- Checked with other users in the office, similar configs, but no-one else has same problem
- I usually manually add the 'reply to' address when composing emails now, this appears to help but not will all networks.

I'm very confused, I try tackle the problem every few weeks and then give up.

Any advice would be great and rewarded with virtual hugs and cups of tea :-)