Update Set-MailContact.md

-UserCertificate and -UserSMimeCertificate parameters are now supported for Set-MailContact similar to Set-User.

@chrisda to review

Author: paisvivekanand

exchange/exchange-ps/exchange/Set-MailContact.md

@@ -84,6 +84,8 @@ Set-MailContact [-Identity] <MailContactIdParameter>
  [-UMDtmfMap <MultiValuedProperty>]
  [-UseMapiRichTextFormat <UseMapiRichTextFormat>]
  [-UsePreferMessageFormat <Boolean>]
+ [-UserCertificate <MultiValuedProperty>]
+ [-UserSMimeCertificate <MultiValuedProperty>]
  [-WhatIf]
  [-WindowsEmailAddress <SmtpAddress>]
  [<CommonParameters>]
@@ -1527,6 +1529,38 @@ Accept pipeline input: False
 Accept wildcard characters: False
 ```
 
+### -UserCertificate
+The UserCertificate parameter specifies the digital certificate used to sign a user's email messages.
+
+```yaml
+Type: MultiValuedProperty
+Parameter Sets: (All)
+Aliases:
+Applicable: Exchange Server 2013, Exchange Server 2016, Exchange Server 2019, Exchange Online, Exchange Online Protection
+
+Required: False
+Position: Named
+Default value: None
+Accept pipeline input: False
+Accept wildcard characters: False
+```
+
+### -UserSMimeCertificate
+The UserSMimeCertificate parameter specifies the S/MIME certificate that's used to sign a user's email messages.
+
+```yaml
+Type: MultiValuedProperty
+Parameter Sets: (All)
+Aliases:
+Applicable: Exchange Server 2013, Exchange Server 2016, Exchange Server 2019, Exchange Online, Exchange Online Protection
+
+Required: False
+Position: Named
+Default value: None
+Accept pipeline input: False
+Accept wildcard characters: False
+```
+
 ### -WhatIf
 The WhatIf switch simulates the actions of the command. You can use this switch to view the changes that would occur without actually applying those changes. You don't need to specify a value with this switch.