Hi,
Using the same Outlook account on several devices is not, by itself, a reason for your emails to be classified as spam. Outlook's filtering can consider factors such as sending IP, domain, authentication, content, and recipient spam complaints.
First, determine whether the problem is with your account or with the recipient's mail system:
Send a test email to another personal account, such as Gmail or another Outlook.com account.
Ask the recipient to check both Inbox and Junk/Spam.
Send a test email to yourself and reply to it. Microsoft also recommends this as a troubleshooting step for Outlook.com sending issues.
Keep the email simple when testing: normal subject, plain text, your name/signature, and no unnecessary links or attachments.
Make sure your account has not been compromised. Review recent sign-in activity and change your password if anything looks suspicious.
If only one employer/domain is placing your messages in Junk, ask that recipient to add your address to their Safe Senders list. Outlook supports Safe Senders for addresses and domains.
If messages are consistently being classified as spam by multiple unrelated recipients, the issue may involve sender reputation or authentication rather than the number of devices you use. Microsoft notes that sender reputation can be affected by sending IP, domain, authentication, and complaint rates.
For job applications, also make sure your display name and email address are professional and avoid sending the same message repeatedly to many recipients in a short period.
If you can provide the exact email address/domain you are sending from (you can redact the username), whether recipients are using Outlook/Gmail/company email, and whether the messages bounce or simply appear in Junk, the cause can be narrowed down further.