How is a Mac user accessing my email and job seeker app?

This is not a question of your iPhones security – as you alluded to In your other thread.

How does a Mac have access to my iPhone 1… - Apple Community

The person in question probably has no access to your iPhone. However, it sounds like they are trying to get into your Indeed account, and to change the e-mail address associated with it.

If this person knows the user name you use with Indeed (which is probably your e-mail address), they could try to get into your Indeed account on any platform that Indeed supports - whether that be an iPhone, Android phone, a Windows PC, or a Mac. If they knew your Indeed password, they could actually get in, and even if they didn't, they might be trying to reset your password, resulting in Indeed sending you e-mail to ask for confirmation.

If you did not request a password change or e-mail address change, do not confirm the change. You could contact Indeed to report unwanted attempts - though to be on the paranoid/safe side, it would be best to contact them using official contact information known to be good, rather than any link or number provided in the message you got. Such a message could be legitimate, or could be a counterfeit that is part of a scam designed to "phish" for your information.

• What are you seeing where a Mac user is continually trying to sing onto your email?
• Are you seeing an email that is telling you this?
• Did you recently fall for one of the Indeed job scams where someone wanted to interview you on the Signal app?
• Have you changed your Indeed Password yet? You may even want to change the email address used for indeed.

https://support.indeed.com/hc/en-us/articles/39462136433677-Changing-Your-Account-Email-Address-and-Phone-Number#h_01K4ST19SHVN0T54XA53V48VFY

And a side note, never use the same password for 2 different accounts.

My guess is that the person trying to get into your account was doing so using a Web browser on a Mac, an iPhone, or an iPad. Indeed guessed that the person was using a Mac, based on the browser's user agent string (e.g., identifying it as Safari).

Then, assuming that they sent a security alert to you, it may have said that the person who tried to log in or to reset your Indeed account was on a Mac, to help you determine if that was you – or a stranger.

If you don't own a computer or a Mac, you should indeed (no pun intended) find that suspicious. But it doesn't mean that the person has access to your phone.