MIME filtering problem

Question

Hello, 
 I am trying to allow .xslx files through the MIME filter. I have whitelisted all excel file types in the firewall, however it is still blocking certain .xslx files If I send one to my client, it goes through. However, when they get sent .xslx files from their vendors, the MIME filter is blocking them for some reason. 
 
 I cant figure this out. 
 
 bounceback: 
 "MIME-Filter has removed this attachment. Filtered by filename extension: Spreadsheet (2).xlsx"

Attila Kepenek · Answer

Hello Matt, 
 I am faced the same issue . First we thought it Exchange Antispam issue. 
 But it is because sophos default antispam policy. We have selected some extentions to block but not office documents. Even if we don't select office document extensions , sophos was blocking excel files. When we select the extensions to none , excel files not blocked. 
 We inform sophos about that, it may be bug. 
 Regards,