TS3988 I cannot change the incoming mail sever

Question

I recently set up two aliases through iCloud and then added them as new email accoutns to my email client on my computer. However, I cannot click on the field to change the incoming mail server. There is a generic greyed out 'mail.example.com', but I cannot change that on either account. I also have squiggly lines nest to the inboxes on the email client. When I click on those, I am asked to put in a password. The only password I know to put in is my iCloud Password, but that doesn't work, and it asks again.
Can anyone please help?
Thanks,
Jeremy

Answer 1

I am up against the same problem with a reticent Incoming Mail Server field as I attempt to set up IMAP accounts for my original mac.com alias addresses. I've tried deleting the incomplete account setups, then recreating an identical account using "imap.mail.me.com" without success. Nor have I found any improvement by changing the Account Type from an iCloud IMAP to a plain IMAP account…and back again.
The field labeled Alias appears to offer a choice of Custom or Edit Aliases but attempts to make a different selection are futile…the setting remains on Custom.
Curiously, however, my primary mac.com address appears to be operating correctly, though it requires an altogether different IMAP address — po3-imap.mail.me.com.  Presumably, a solution exists; however, it remains elusive and far from intuitive to this observer.  Any insight from more experienced users than I will be gratefully received! Thank you.
n.b.:  a conversation with an AppleCare specialist left him equally perplexed and questioning whether a mac.com alias email address can, indeed, be set up in iCloud to work alongside ones primary mac.com address.