I have an address at mail.com that I give out when people ask me for one. It's personalised and I like it and it's programmed to forward to my Plusnet one which I access via Mail, the standard Mac email client. Your comment has made me realise I've never tried to add the mail.com address to the accounts in Mail for Mac. I'll give that a go, see if it works.
Be aware of Plusnet's webmail though. If you have it set to remain on the server after downloading in your IMAP settings it can take forever to go through them and delete once the mailbox gets full. Their tech guys have acknowledged that this slowness is an issue and they don't seem to be doing much about it. I've set it up to delete from server on download but that means that the mails only download to one device which is little better than POP really.
Unless I'm really misunderstanding things which is a distinct possibility!