Memo fields are designed to hold large pieces of text. They are essentially unlimited in length. However, remember that email-list memo fields require that the text be formatted in a particular way. If you attempt to put a value into the field which does not match the predefined rules, the assignment will be unsuccessful. Also, even though an HTML memo field will accept plain text and a plain text memo field will accept HTML, putting the wrong type of value in the field will make it display in an odd way.

One other strange behavior is how empty memo fields behave. When the empty-string "" is stored to the Relate database it comes back from the database as a null. But to make things even more confusing, when a null String is inserted into an edit field on a form it comes back as the empty-string. Of course, you can't always predict whether the memo field was just part of a form because the current user may not have permission to edit the field or the form may have been partially updated via an editable merge report. So, to make a long story short, if you are looking for empty memo fields that may have just been edited on a form, such as in a field formula, you must check for both null and "". But if you are dealing with a memo field which definitely just came from the database, such as in a merge report formula, you only need to check for null.  Fortunately there is a function designed for this exact purpose, nullOrEmpty(...).