For understanding this correct, with literal addresses meant "username@192.168.0.1".

Not exactly, the literal addressing is username@[192.168.0.1] Here's the section of RFC 532, the standard for handling server to server transactions.

4.1.3.  Address Literals

   Sometimes a host is not known to the domain name system and
   communication (and, in particular, communication to report and repair
   the error) is blocked.  To bypass this barrier, a special literal
   form of the address is allowed as an alternative to a domain name.
   For IPv4 addresses, this form uses four small decimal integers
   separated by dots and enclosed by brackets such as [123.255.37.2],
   which indicates an (IPv4) Internet Address in sequence-of-octets
   form.  For IPv6 and other forms of addressing that might eventually
   be standardized, the form consists of a standardized "tag" that
   identifies the address syntax, a colon, and the address itself, in a
   format specified as part of the relevant standards (i.e., RFC 4291
   [8] for IPv6).

   Specifically:

   IPv4-address-literal  = Snum 3("."  Snum)

   IPv6-address-literal  = "IPv6:" IPv6-addr

   General-address-literal  = Standardized-tag ":" 1*dcontent

   Standardized-tag  = Ldh-str
                     ; Standardized-tag MUST be specified in a
                     ; Standards-Track RFC and registered with IANA

   dcontent       = %d33-90 / ; Printable US-ASCII
                  %d94-126 ; excl. "[", "\", "]"

   Snum           = 1*3DIGIT
                  ; representing a decimal integer
                  ; value in the range 0 through 255

   IPv6-addr      = IPv6-full / IPv6-comp / IPv6v4-full / IPv6v4-comp

   IPv6-hex       = 1*4HEXDIG

   IPv6-full      = IPv6-hex 7(":" IPv6-hex)

   IPv6-comp      = [IPv6-hex *5(":" IPv6-hex)] "::"
                  [IPv6-hex *5(":" IPv6-hex)]
                  ; The "::" represents at least 2 16-bit groups of
                  ; zeros.  No more than 6 groups in addition to the
                  ; "::" may be present.

   IPv6v4-full    = IPv6-hex 5(":" IPv6-hex) ":" IPv4-address-literal

   IPv6v4-comp    = [IPv6-hex *3(":" IPv6-hex)] "::"
                  [IPv6-hex *3(":" IPv6-hex) ":"]
                  IPv4-address-literal
                  ; The "::" represents at least 2 16-bit groups of
                  ; zeros.  No more than 4 groups in addition to the
                  ; "::" and IPv4-address-literal may be present.

If they want not setup the server accepting literal addresses, which tools available to forwarding mails this way?

There are none.  You can remove this domain from your local domain if you are not receiving mail via MercuryS and then Mercury core would resend the mail off the server using MercuryE to the other server.

Hello,

I've configured Mercury/32 with mercfwd.dll:

daemon:c:\mercury\mercfwd.dll;[yyy.yyy.yyy.yyy]: somedomain.tld

Mercfwd is forwarding all mails of @somedomain.tld correct...

But the Problem is, the answering mailserver only accept mailaddresses

in form of  @somedomain.tld..

How can this work, redirect @somedomain.tld to another server with the correct domain @somedomain.tld ??

Thanks for any input..

daemon:c:\mercury\mercfwd.dll;[yyy.yyy.yyy.yyy]: somedomain.tld

If the receiving host does not support literal addressing you cannot use any of the tools to forward a domain to another server.  The basic problem is that mail for this domain is currently being received by Mercury using that domain and so it must be changed so that Mercury core sends it off the server.  You might talk to the people on the receiving end and ask them to setup their server to accept literal addresses.

For understanding this correct, with literal addresses meant "username@192.168.0.1".

If they want not setup the server accepting literal addresses, which tools available to forwarding mails this way?