Hi Sharath,
Maileater is based on the pdm_text_cmd interface, for which all the "updateable" variables are in the textapi.cfg file which you can find under the NX_ROOT\site directory. If the variable exists in the textapi.cfg, then you can update it using maileater by specifying that attribute and its value. However, keep in mind that the CI-to-ChangeOrder relationship is many to one - meaning a Change Order can have multiple CIs on it - thus the reason for the LREL usage there. So I am not sure if this can be done, because I believe that all of the attributes in the textapi.cfg file are single one-to-one relationships, but you would have to test it out.
Thanks,
Jon I.