Knowledge Base
File extensions that are not allowed as attachments
From a security perspective, the mail server rejects inbound emails that contain attachments with any of the following file extensions:
| .386 | .fon | .ocx |
| .ade | .fxp | .ops |
| .adp | .hlp | .ov |
| .adt | .hta | .pcd |
| .app | .htr | .pgm |
| .asd | .inf | .pif |
| .asp | .ini | .pl |
| .asx | .inp | .pm |
| .bas | .ins | .prg |
| .bat | .isp | .scr |
| .bin | .jar | .sct |
| .btm | .jse? | .shsb? |
| .cab | .keyreg | .shs? |
| .cbl | .ksh | .slb |
| .cbt | .lib | .smm |
| .cgi | .ink | .swf |
| .com | .mda | .swt |
| .cil | .mdb | .sys |
| .cla(ss)? | .mde | .vbe |
| .cmd | .mdt | .vbs |
| .cpe | .mdw | .vbx |
| .cpl | .mhtm | .vir |
| .crt | .mhtml | .vmx |
| .csc | .msc | .vxd |
| .csh | .msi | .wmd |
| .css | .msp | .wms |
| .cvp | .mst | .wmz |
| .dll | .mp3 | .wsc |
| .dot | .nte | .wsf |
| .drv | .nws | .wsh |
| .exe | .obj | .xms |
| .chm | .js | .lnk |
| .reg | .url | .eml |
Why Are These Attachments Blocked?
To protect users from potential viruses, malware, and harmful software, the mail server does not allow:
- Blocked file types in compressed formats (such as .gz, .bz2)
- Blocked files embedded inside archives (such as .zip, .rar, .tgz)
- Documents containing malicious macros
- Password-protected archives that contain another archive
Note: Emails with attachments exceeding the allowed size limit will also fail to send.
What you can do
If you're sure the file is safe, you can ask the sender to upload the file to Google Drive or ZIP/RAR files and add them as attachments.
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