Being a bit of a pedant here, but you aren't "receiving" mail via POP3, you are "retrieving".
The sending and receiving (i.e. transfer) are both part of SMTP.
If you want to self host your own mailboxes (e.g. IMAP/POP3) you will need some way to get the mail into them (mail delivery) which is also (usually) SMTP.
But your point definitely stands - You can handle the inbound side and outsource the outbound mail delivery issues.
The sending and receiving (i.e. transfer) are both part of SMTP.
If you want to self host your own mailboxes (e.g. IMAP/POP3) you will need some way to get the mail into them (mail delivery) which is also (usually) SMTP.
But your point definitely stands - You can handle the inbound side and outsource the outbound mail delivery issues.