Helmut Koester's view:
Romans 16 is a letter of recommendation, the earliest letter of recommendation for a Christian minister, and it's written for a woman, Phoebe, who is, in the beginning of the chapter, said to have been a deacon, not a deaconess -- but a deacon in the sense of a preacher, a minister, because Paul uses the same word for himself. He calls himself, in a number of instances, a deacon of the new covenant in 2 Corinthians.
It's the male form not even the female form that is used in Greek here. The other word that is used for Phoebe is a Greek word "prostatis." Now if you go into the general dictionary of Greek, it will say "prostatis" has two meanings: "1. president, and 2. patron." Now an Old and New Testament dictionary which is no longer in print said "prostatis" means "1. president, 2. patron, 3. helper," in parenthesis, "(only in Romans 16:1)." And that's the translation that has existed for a long time. I think it has now disappeared from The New Revised Standard Version.