- thunderbird has filtering ability to move or copy incoming messages to other folders - if the outlook account is IMAP, setting it up in thunderbird will display the same folders - thunderbird can import csv or ldap contact lists - your concern about having different input and output email addresses is confusing, as most email servers check to see that the email address in smtp server is the same as the sending account and reject inconsistencies. So, it is not a thunderbird requirement, but an internet anti-spam monitoring issue. My guess what you wrote isn't what you meant.

David, Thanks for the reply.

In my case, I still have my email client on my PC setup as POP3 not IMAP so all of the emails I have in folders are stored within my .PST file. Can Thunderbird somehow migrate these old emails?

In regard to having different email address configurations in the inbound and outbound settings it is possible and I've had this configuration setup for years not only on my PC but also on my Android email clients. The original rationale is that you have a public email address and a private email address. In this setup you receive emails sent to your public address and then automatically forward all email to your private email address. What happens is that outlook.com actually scans all messages before they are forwarded then upon receipt the private email provider scans them a second time for spam with the end result being a very clean inbox of messages. Most people that do this simply use the SMTP server of the private email provider when they send messages but you have to configure that private email to say the message is actually coming from the private email address. The only problem with that technique is that if the person receiving the message examines the full message and looks at the email headers, the actual address of the private email address will be exposed. So, if you configure the outbound SMTP server settings to use your public address then the message will only display the public address sender information. I know it's a weird setup and probably overkill but it works. Currently, I'm using Outlook 365 as my email client but that client does not have the capability to use OAuth2 and and I'm trying to determine if that client doesn't need it since Outlook 365 is a par of my Microsoft 365 subscription. In the mean time I've found that Thunderbird can be setup with different inbound and outbound configurations and use OAuth2. Hope this explains my weird setup.

I suggest trying to see if what you want works. Thunderbird is extremely flexible.