OK, one more question about sending email TO an old VAX

I am confident DNS is set up correctly. I have another vax server sitting next to the microvax3100 that is using a diff. subdomain on vintagecomputer.net and this vax sends and receives mail without issue. The only diff between the 3100 and the other vax server is the other is running a newer version of multinet and vms. All configurable multinet settings are set the same, other than the FQDN for the mail server itself. I can telnet into both servers using the subdomains. No special email address formatting is needed to send and receive email between the outside world and the other vax server (a 4000). If I want to send FROM the 3100 VAX I need to format the address as: MAIL> MAIL To: SMTP%"bill at myemail.net" Works fine. If I reply to the received message however, the postmaster of the VAX does receive the message but rejects the address FORMAT, bad address. The postmaster sends the external sender a rejection email: Bad address -- Error -- %MAIL-E-USERSPEC, invalid user specification ':' So, my question is ... If when sending from a modern Internet smtp mail client do I have to use a special address format so my to a VAX running the older vms/multinet can deliver it. For example, something like System <%"system at microvax3100.vintagecomputer.net"> It seems like the trick is how to format the header of the message. As I said before I can use php to make a custom header if I knew the trick to formatting. Hope that clarifies Bill