Здравствуйте, E_g_0_r, Вы писали:

E__>Поддерживает ли почтовый клиент Lotus Notes MAPI?

E__>При клике в IE на mailto:... создается пиьсмо в Lotus.

E__>Однако, при попытке использовать программно MAPISendDocuments возвращается
E__>ошибка MAPI_E_NOT_SUPPORTED.

E__>Какой способ мог бы быть универсальным для разных клиентов (Lotus Notes, Outlook, The Bat)?

Вот выдержка из хелпа Lotus`а (поиск в хелпе слова MAPI)
You can use mail-enabled Microsoft programs to work directly with your Notes mail on a Domino server. For example, you can use such applications as Microsoft Word or Excel to access Notes/Domino mail and directory services. To do this, you first need to set up a profile that lets you use the Notes Service Providers for the Messaging Application Programming Interface (MAPI).
Note Microsoft Outlook is also a mail-enabled application, and you can use the procedure below to set it up for sending Notes mail, as long as you are not already using IBM Lotus Domino Web Access for Microsoft Outlook.
For more information, If you have installed Lotus Domino Administrator 6.5 Help, see Domino Web Access for Microsoft Outlook. Or, go to the Documentation Library on the Lotus Developer Domain to download or view Lotus Domino Administrator 6.5 Help.