Why does a reddish hue show up in Mail at times?

The idea of testing in a new User is to see the account in Mail without your others folders etc in Mail. Once you see that it works, you should be able to go back to your User and remove the Comcast account and setup correctly. If you still have problems with the account, I would do a clean install of your Mail data folders. It's possible that if you add Gmail to a corrupted Mail folder you would have similar issues.

I'm guessing you have used Comcast email for many years. You can forward your account to Gmail or whatever email account you choose so you will receive your emails.

When I was with Comcast, they didn't even offer IMAP (about 2 years ago).

As for Yahoo: accounts: they are very prone to be hacked into; I've had mine hacked into several times resulting in mega spam emails (some with very objectionable and specific subject lines even though I indicated that I was a 95 year old male which would make me about 105 by now, LOL). But they did steal my email address as a 'from' address and are using it to send out spams to make them look legit - I am actually getting spam FROM me TO me. When you set up an account, you should immediately find your preferences and account settings as there is a page buried down deep that deals with marketing preferences. Best to UNcheck them all or you will be bombarded with spam and you need to do that immediately or Yahoo will 'share' (sell?) your email address promptly.

Gmail is a Google product; as such they read all your emails in order to 'tailor' their ads - you mention to a friend that you will be going fishing and subsequent ads will have appropriate content. I do not use any Google product.

I do not trust either, but do use Yahoo as my general junk mail account - using it for everyone who insists they want an email address whether they need one or not. I have found two that are somewhat more concerned about their subscribers' privacy:

http://www.gmx.com/

And fastmail.com - can't seem to post a link as I keep getting my own inbox there rather than a generic page.

you wrote:

... Either way I plan to set up a new email - in terms of security do you have any input in using either Yahoo or Gmail? ...

I have both. GMail only recently. Yahoo for almost two decades.

Yahoo

• YMail has a very robust SPAM filter - I have no received any SPAM at all * in my Mac Mail client - MS ENtourage " - the SPAM folder on the WebClient is often chock full though
• FEW 'false positives' - rare occasion that the filter makes a mistake on legit emails... it applies "first in, first out" cleaning regimen, so any that may get misfiled are there for ±30 days
• No evidience at all of being hacked
• my UserName is very uncommon, so doubtful that any person or program could 'guess' it for nefarious purposes - but then again, my SPAM folder chock full.

GMail

• as I said, very recent - it is IMAP and did not seem to want to play nice with Entourage, freezing in 'checking for new mail' only on the subsequent to first check at launch. As it is new and not mission critical, I workaround the problem by removing that from the periodic "Send and Receive All" schedule.
• I have had no SPAM on it at all - at least that I have not had any make to Entourage and my "Junk email" folder is empty on the WebClient

A long time ago, i had a secure-encrypted paid account that only other users of the service could read - I let it go after the need for it passed into oblivion.

I wonder if iCloud mail aliases might suit you? Ge an email account at say Yahoo with a COMPLEX username "antidisestablishmentarianism @ example.com" (or somesuch) as a Primary Apple ID email...

iCloud: Create or change email aliases - Apple

Jun 11, 2015 - If you use email aliases that end with @mac.com or @me.com, you ... On an iOS device, go to Settings > iCloud, turn on Mail, then follow the ...

I agree with babowa about Yahoo. I can't tell you how many users with Yahoo accounts get their accounts hacked. How do I know? I get emails sent to me from their email to everyone in their Yahoo contacts. I can also see all their contacts in the email that also got the email from the hacker.

Gmail has a good spam filter but Gmail is a special kind of IMAP and while Mail has gotten much better with Gmail oddities so it's easier to setup especially since you would be new to Gmail.

iCloud is the easiest to setup and use in Mail. However Apple's spam filter does things in the background and you might have emails that just disappear never to be seen again. If Apple sees it as **** it just goes poof. There is no way to turn this off since it happens on the server side.

Microsoft's free account is outlook.com. Surprisingly, it's one of the better services. It used to be called msn.com, hotmail.com, live.com

Also, I plan to reinstall Mail. I'll have to figure out how to save my local folders, do the re-install, then load them back.

This should be in another post. Since this post has been marked as answered, none of us here that are helping you will get any credit for doing so. In addition anyone looking for how to start with a clean Mail profile will not find it under the current subject of reddish hue.

Also, I plan to reinstall Mail

As Mail is an OS component, you would need to reinstall the entire OS - either on top of what you have (which will not get rid of any corrupt files if there are any, but will leave all your folders intact) or, using internet recovery, you can erase your disk and then install a fresh copy of the original OS version. In this case, you'd lose everything of course, so having a good backup (or two) is absolutely essential. During that setup, Setup Assistant would automatically pop up and ask if you wish to restore from another source and you can choose your Time Machine (or whatever) backup at that point.

I doubt he needs to reinstall the Mail app. Mail works in a new User. It's the mail data folders & preferences in his User's folder that need to be wiped clean.

Well, the .plist can easily be deleted and it will regenerate itself. I must admit I do not know if one deletes the contents of the Users > Library > Mail > MailData folder contents if they are re-generated automatically. Also do not know what you mean with 'not getting credit for helping' - I thought we were all volunteers here (except for the few Community Specialists and Hosts).

We are volunteers. It's Apple that setup the points system.

Ahh, didn't realize that is what you are referring to since we are not allowed to ask for/allude to the system unless asked. Also because I pretty much ignore an inherently pointless system.

I have a red screen display. The system Preference > Accessibility > Reduce Transparency worked perfect and cleared up the soft red behind my mail messages.