１． 伊朗中央银行因外汇原因，通知个商业银行从五月三日起停止开立信用证；
２． 这临时措施，新的进口政策一订，这个措施可能取消；
３． 希望对方随时告知有关情况。
按照这三点，适当地划分段落，把信重新改写如下：
It is reported that the Iranian Central Bank has instructed the commercial banks to suspend their issuing new Letters of Credit as from the 3rd May because of its decreasing foreign currency funds.
Furthermore it is said that the suspension seems a temporary one and will be released with establishment if a new import policy.
We are much concerned, however, about the outcome of this movement toward restriction of import to Iran. We, therefore, shall be obliged if you will keep us well informed of development of this new state of affairs, especially in connection with imports from France.
修改过后的段落并没有增加或者减少任何一个词语，也没有改变原来句子的意思或者表达方式，只是按照意思将其恰当地划分了段落。较之原文，修改后的信函读起来比较清楚易懂，看起来也很简练，更加容易让人接受。