Is it possible to use these Swedish letters? If I type them in the email body the email from the dispatcher they come out as question marks.
Seems like a bug. I posted to github - https://github.com/blynkkk/blynk-library/issues/56. Thank you for reporting.
It is not the library bug. The library handles all strings as UTF8 Unicode.
In general, you can try to print your message to serial and see if it works (the terminal should be set to UTF-8 encoding).
If it doesn’t, probably you should read about unicode support of your compiler…
How was that solved? I got the same problem with German umlauts.
What was the cause for it?