Is emotional conversation between a married woman and a non-mahram man considered a major sin?

Emotional speech with a foreign woman is forbidden, and the one who engages in it commits a sin. It is one of the means that lead to zina (unlawful sexual intercourse). Although it is not a major sin, persistence in minor sins can turn them into major sins that destroy their perpetrator. "There is no major sin with seeking forgiveness, and no minor sin with persistence."

The Messenger of Allah, peace and blessings be upon him, likened the belittled sins to a group of people who camped in a land, and each one of them gathered a stick until they lit a fire that cooked their food. One should not look at the smallness of the sin, but rather at the greatness of the One Whom he disobeys.

And Allah knows best.