SYMPTOMS

Clients cannot relay through server and some clients cannot send to server.

CAUSE

The cause is the IME_SYSTEM, IME_ADMIN or system account whichever the SMTP service is running under does not have access to the extensions key in the registry (HKLM->Software->MailEnable->MailEnable->Connectors->SMTP->Extensions).  

The result of this permission deficiency can be found in the MailEnable logs and would mean that none of your clients will be able to relay through the server.  The logs entry will be displayed after the EHLO command like the entry below;

Date Time    SMTP-IN    Message ID.MAI    956    xxx.xxx.xxx.xxx    EHLO    EHLO [xxx.xxx.xxx.xxx]    250 [xxx.xxx.xxx.xxx] This server does not offer any extensions    62    21

RESOLUTION

To fix this open the registry using the REGEDT32 command (Start->Run->regedt32) and give the IME_SYSTEM (or account running the SMTP service) full control of the following key;

HKLM->Software->MailEnable->MailEnable->Connectors->SMTP->Extensions

You can also verify this by using the telnet command to the server and then typing EHLO after connection as the returned result will be "This server does not offer any extensions" if you are affected by this permission deficiency.

REFERENCES

http://www.mailenable.com/kb/content/article.asp?ID=ME020207