Issue Change mail server name

[bax]

Hello

I am having an issue regarding changing the mail server name. I am not very technical but I can see the email DNS records in PLESK are pointing to the right IP and have the correct name. However when I click on the "i" icon next to my emails the server name is different - missing mail.xxxxxx and webmail.xxxxx. I am attaching screenshots for reference. Any idea how to change that? Any pointers are much appreciated. Thank you!