Here are some problems that may arise when doing Mail Merge using an .rtf or .docx template:
It is possible that the template is too large. This usually happens because the template contains high resolution pictures. In .rtf documents, pictures are saved in a format that makes them rather large, so a high resolution picture can make the template enormous. Shrink the template by reducing the resolution of the pictures to a more appropriate size; usually 300 dots per inch works well since that is around the resolution of what people can see.
Another possibility is that you are saving many merged documents (for several contacts) into a single .rtf file, and the resulting document is too large. Again the problem may be caused by pictures. If the template contains pictures, then make sure they are as low resolution as possible. Also, if at all possible, put the pictures into the template’s headers and footers; this ensures that the resulting output file contains only one copy of each picture, instead of one copy for each contact.
If Sumac complains about a formula, inside angle brackets <<…>>, but the formula works fine in Sumac’s Make Template window, or when you use it in a text-only template, then the problem is probably embedded formatting codes. Some document editors (e.g. Word) insert invisible codes into your documents. Sometimes it inserts these codes in the middle of your formulas. So even though it looks like <<c_Name>> (which is correct) on the screen, it may actually be << c_XXname >> (which is incorrect), where XX is some embedded command which Word does not display on the screen. The way to fix this problem is to type the entire formula in a plain text editor (e.g. Sumac’s Make Template window, or Notepad on Windows, TextEdit on Macintosh), then copy the formula, from before the opening angle bracket to after the closing angle bracket, and paste it into your .rtf or .docx template as a single piece.