I have a company, I will call XYZ, that is using SBS and they use Exchange server for e-mail. Everything is working OK except when they send e-mail to this one and only this one company, I will call this company ABC, they get a 5.1.1 error stating that “The account does not exist at this organization this message was sent to”. This message is generated by Company XYZ exchange server. Any e-mail sent to any person at Company ABC is not delivered and we get the same 5.1.1 code. Now here is what is strange. If you send Company ABC e-mail from any other source out side of Company XYZ the e-mail will arrive. Company XYZ has no problems with other companies.
Company ABC is using POP 3 accounts to get their e-mail and their ISP states nothing is wrong on their end as other people can send mail to ABC.
Company XYZ is setup using a Smart Host to their ISP. I call this ISP and ask them to send Company ABC a test e-mail. I knew ABC would get it but I wanted to be sure and sure enough ABC got the e-mail.
I’m thinking that something is wrong at Company ABC ISP and may be a reverse lookup problem of some sort.
My question: Is their something I am missing on XYZ Exchange server that can cause this problem?