In short, the answer would be no.
But truly, this question deserves clarification. So, let me explain why why I’ve given such an answer.
Before I say anything more I’d like to preface my explanation by saying: Once you are married your spouse becomes the number one person in your life to whom you are consecrated by God. They should be number one in all things, and should never feel like they have a contestant for your affections, especially with someone of the opposite sex. This consecration demands just sacrifices and is wholly deserving of such fidelity. Giving your deepest affections to your beloved should not be difficult for you. You should be eager, in fact. They are the one person for whom you should want to “forsake all others”. They should be the recipient of your deepest love, devotion, passion, and affection — and that without reservation.
Once you are in a committed relationship or espoused to be married the boundaries of relationships change. All relationships are going to experience necessary adjustments. However, the element of affection is only one variable in the equation. There are also the relational elements of time, frequency, distance, emotional investment, etc., all which are subject to change once we marry. That being said, friendships can often take the hardest hit. Marriage inherently requires such sacrifices of time, distance, and affection with our friends. And yes, they will feel it. It may be hard for them to understand if they are not married. However, if they are married, they should respect it and understand it readily. It’s part of being consecrated to your spouse and building a life together. The adjustments required can sometimes be quite drastic or even painful at times. If others do not understand this (many times because they are not married), you’re going to have to respectfully enforce the boundaries of your marriage very patiently without feeling guilty or letting down your guard. If people cannot respect your marriage boundaries, you may need to let them go or cut them loose entirely. Simply said, sometimes relationships that were perfectly healthy and appropriate as a single individual are no longer appropriate or viable within a marriage covenant.
If your friends are married as well, it’s much easier for these boundaries to fall into place. But friendships are especially sensitive, I believe. Reason being, these are relationships we choose. For that very reason, many times they are closer than any blood relative or next of kin we may have. The ties can go very deep, and the investments can be life-long. But once you’re married, time spent together becomes briefer, and perhaps more seldom, and those times together often have stricter boundaries. Thus, the emotional investments are a bit more measured as well.
Men and women do have platonic friendships. It happens. However, it’s not the norm. Rather, it’s the exception. Young individuals frequently have friends of the opposite sex in high school and college. That’s to be expected. That is a very welcome and normal part of growing into adulthood. But once we reach maturity friendships with the opposite sex usually go either one of two ways: (1) they progress toward romance or (2) they fall away entirely. And if neither is true, I would question the quality of the friendship and on what terms it was actually bred. Is this individual worth the risk of your marriage or the offense of your spouse? The answer should always be no. Absolutely. Every time. If the answer is not “no”, you need to be asking why.
Your spouse should never have a contestant. Ever. If your affections are not so resolved, it is best to rethink being married.
So again, in response to this question, I cannot think of one reason that would justify keeping a friendship with the opposite sex once you are married. And it should stand true that the boundaries and investments of such a relationship would not warrant it worthy of continuing if you are married. You should not only be willing to let it go. It should happen naturally without the pain of regret.