I found that none of the previously offered solutions worked for me in Windows Vista. So, I dug into the Zimbra source files to find out why.
Zimbra uses a variable named zimbraMailSignatureMaxLength to limit the length of the HTML signature you can use. There seems to be no logical reasoning behind this limit and increasing it doesn't seem to have any negative side effects. This variable needs to be changed in
multiple files in order for the maximum limit warning message to go away. Just increase the number I've highlighted in bold below for the line I specify in each file to increase the limit. For my needs, I changed it to
10240 and that was good enough for my signature to not exceed the limit. Here are the file locations and the lines in those files that you will need to modify. This is for the 7.01 version, but should work for some previous versions as well.
C:\Users\YOURUSERNAME\AppData\Local\Zimbra\Zimbra Desktop\conf\attrs\zimbra-attrs.xml
(
NOTE: In XP it would be "C:\Documents and Settings\YOUUSERNAME\Local Settings\Application Data\Zimbra\Zimbra Desktop\conf\attrs\zimbra-attrs.xml".)
<attr id="454" name="zimbraMailSignatureMaxLength" type="long" min="0" cardinality="single" optionalIn="account,cos" flags="accountInfo,accountInherited">
<defaultCOSValue>
1024</defaultCOSValue>
<desc>maximum length of mail signature, 0 means unlimited. If not set, default is 1024</desc>
</attr>
C:\Program Files\Zimbra\Zimbra Desktop\jetty\webapps\zimbra\js\NewWindow_2_all.js
name:"zimbraMailSignatureMaxLength",type:ZmSetting .T_COS,dataType:ZmSetting.D_INT,defaultValue:
1024}
C:\Program Files\Zimbra\Zimbra Desktop\jetty\webapps\zimbra\js\Startup1_2_all.js
name:"zimbraMailSignatureMaxLength",type:ZmSetting .T_COS,dataType:ZmSetting.D_INT,defaultValue:
1024}
C:\Program Files\Zimbra\Zimbra Desktop\jetty\webapps\zimbra\js\zimbraMail\prefs\Z mPreferencesApp.js settings.registerSetting("SIGNATURE_MAX_LENGTH", {name:"zimbraMailSignatureMaxLength", type:ZmSetting.T_COS, dataType:ZmSetting.D_INT, defaultValue:
1024});
Restart Zimbra Desktop after making these changes. You should now have a much larger HTML Signature limit of 10KB instead of the default of 1KB. It's also worth noting that when you install an update for Zimbra it is very likely that it will overwrite these changes. So, you will need to go back and edit them again. Hope this helps anyone else fighting with this issue.