Try to read the forum here. An user called @BraveDude8 claim that you can ask to the support center (support@mangadex.org) to change it. They not make this basic feature available to prevent the spammers abusing it.
MangaDex Forums
Evans01
Basic_human
@BakedBanana you think my situation can be solved if I try to ask those mod?
BakedBanana
The one you were talking about yesterday? Maybe. You would have better luck probably getting in contact with the higherups on Discord.
@Basic_human
The one you were talking about yesterday? Maybe. You would have better luck probably getting in contact with the higherups on Discord.
Basic_human
D'oh
Evans01
Thank you for the latest update, @BakedBanana 