The etiquette for addressing members of the Christian clergy can be confusing. Fortunately manners have been simplified over the years. While the title "Rector" and "Vicar" still exist, the difference between rectors and vicars was essentially abolished in 1936. Both terms refer to priests, so the same rules of address apply, simply using the given title of the individual member of the clergy. There are etiquette proscriptions for addressing a vicar in person and in writing.
Address an envelope to the vicar with "The Reverend" followed by his or her first name and surname. For example, "The Reverend Richard Jones." Capitalise the "R" of "Reverend."
Use "Mr" or "Mrs" to refer to the vicar's husband or wife when writing. For example, "The Reverend Richard and Mrs Jones."
Use this same form when writing an invitation to an event. Use the same wording on the invitation and on the envelope containing it.
Start a letter with "Dear Rector" or "Dear Vicar" if you know the person in question; for instance if he is the clergy person for the parish in which you live and worship. Alternatively, begin the epistle with "Mr," "Mrs," "Ms" or "Miss" as appropriate.
End your letter with the words "Yours sincerely." Sign your name underneath. Modern style guides do not require a comma after "sincerely."
Say "The Vicar" or "The Rector" when referring to the individual in the third person for the first time during a conversation. You could add the surname if it eliminates confusion. After the first reference, refer to the vicar as "Mr" or "Mrs."
Use "Vicar" or "Rector" when addressing the individual directly during conversation. Some vicars may prefer the word "Father." This is a personal choice and is not a required form of address.
There is no proscribed form of address when both people in a married couple are vicars. Crockford's, the UK clerical directory, recommends the use of "Reverend" twice. For example "Reverend Richard Jones and Reverend Rachael Jones."