Good day. We mainly work with clients on activesync, but the problem is also on clients over imap. Many people use calendars and do not receive notifications about creating / changing appointments in calendars on iPhone.

I did the analysis and found out that the calendar application receives an event from the mail, processing ics attachments.
Accordingly, Outlook works with plaintext, and Apple itself sends it to base64 and waits and parses correctly in it.
For example, gmail sends its calendars with two ics with different boundaries - one in pure utf, the second in base64, and event notifications come every time.
I tried to send a crafted letter, taking the generated ics code and adding the second one, in base64, and it also starts working.

I couldn’t write the correct code for adding the second ics, because I don’t fully understand the mechanism for parsing attachments and preparing a letter in the SOPE - as if all attachments come with the same boundary
is it possible to add sending the second ics wrapped in base64 when creating a meeting?