I've used Apple Mail for Mac exclusively on my iMac and two Macbook Pros since 2018 with zero issues. Often, symptoms like you describe are either issuesin your IPS's servers, or due to unneeded aftermarket utilities you have installed.
Anti-virus and so-called "cleaning" apps as well as cheap client-side VPNs can cause issues with mail transmission and reading. If someone else set up your computer for you and you are not sure what is or isn't on it, we can help.
If you want a data-driven evaluation in this setting where we can neither see nor touch your computer, please post an EtreCheck report. We can quickly and within the extreme limitations of these forums help you determine what issues are afoot without our playing a protracted game of "20 Questions" with you that could go on for days.
EtreCheck Pro is available here:
https://etrecheck.com/index
The free version will do nicely for this purpose, although the app is worthy of our financial support.
We can see hard data about drive performance, software issues and interferences, and RAM usage. Etrecheck is the development of a long-serving and trusted ASC contributor. It is a reporting app, not a "fix-it” app, expressly for displaying information in these forums to help us help you remotely. It will not reveal any personal or secure information.
Please see this excellent user tip on how to post long text reports like EtreCheck's into a forum response:
How to use the Add Text Feature When Post… - Apple Community
Please post the entire report unedited. What seems insignificant to a new Etrecheck user can hold answers for those of us who have reviewed thousands of those reports.
