Being a Kiwi myself, I thought, Pegasus might be worth a try.
However, I got stuck with the address book. The mail provider I am using for years supports CardDAV (only) as a protocol. Is there any change to synchronize Pegasus Mail with the address book on the mail server? Grateful for every hint in this direction, as for me it will be absolutely essential to work with that remote address book!

Pegasus Mail does not support the CardDAV protocol. I knew nothing about CardDAV until doing a little research. That research found several references to CardDAV and .vcf files. Based on that, there might be a way to import CardDAV data into Pegasus Mail. There would not be a way to keep it synchronized automatically. The conditions required for this to potentially work would be:

• That CardDAV can export to a .vcf file
• That the Pegasus Mail add-on utility called PMvCard could import the data from that .vcf file.

Note that the PMvCard utility is not available for download in the Add-ons for Pegasus Mail section of this site. This was the last post by its author regarding how to obtain any of his add-ons.
https://community.pmail.com/index.php?u=/topic/11684/send-list-of-extensions-by-martin-ireland

A process that I've found that works to convert address box date is to create a file as tab delimited, and using Pegasus Import option.
Created a test addressbook and made a record with data and exported it.
First line is just a comment, * at possition 1.
The other lines are the fields, and should have a tab after each field

• Pegasus Mail Addressbook, Tue, 27 Feb 2024 11:47:31

namexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
email@mailxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
KEYXXXXXXXX Deptxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Phonexxxxxxxxxxxxxxxxxx
Faxxxxxxxxxxxxxxxxxxxxx
Streetxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Postxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Notexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Other options would be tagged delimenated format.

Name: namexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
E-mail address: email@mailxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Key: KEYXXXXXXXX
Of: Deptxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Phone number: Phonexxxxxxxxxxxxxxxxxx
Fax number: Faxxxxxxxxxxxxxxxxxxxxx
Street address: Streetxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Postal address: Postxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Notes: Notexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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