If your users work for different business units or companies within your organisation and you need different signatures depending on which company they are sending an e-mail on behalf of, you can achieve this by using 'Location' documents within your Lotus Notes Client.
e.g. A user within a Domino Evironment can send e-mail from CompanyA.com and CompanyB.com.
The email address used is changed using 'Location Documents' within the Lotus Notes Client.

In the above image the email address is specified in the 'Internet Mail Address' Field. When an email is sent from the Lotus Notes Client this e-mail address is added to the outgoing message in the field 'INetFrom'. This field can then be used in sub signatures.
In the Signature Configuration Database, you can create a 'Common' Signature Block for All e-mails and then use 'Sub-Signatures'
Common Signature block
The screen shot below shows an example of a signature block with two sub signatures added. One for CompanyA and one for CompanyB.

Sub Signatures
For each company a seperate sub signature needs to be created. Each one will have a slightly different formula.

The formula specified above is
________________________________________________________________
@If(@Contains(@lowercase(InetFrom);'@companya.com');@true;@false)
________________________________________________________________
This formula must be entered without carraige returns.
Examples
The two images below show examples of e-mails sent using the above configuration

