Thunderbird complains that attachment has a virus

Question

I tried sending a DLL as itself, in a ZIP and in a ZIP that was renamed.
It is unlikely this file has a virus.
It is Flower.Workflow.dll downloaded from http://flower.codeplex.com/ as part of a a ZIP. The ZIP extracted with no anti-virus complaints.
An error occurred while sending mail. The mail server responded: vVKx1o00G1W8Qfl01 :: auth :: Message rejected for spam or virus content :: Please include this entire message when contacting support :: v=2.1 cv=WOHxXxcR c=1 sm=1 tr=0 p=9sbYPhA4L6soLPksZecA:14 a=4F1iYNGcaRR8aAQ0jNN9Bg==:117 a=4F1iYNGcaRR8aAQ0jNN9Bg==:17 a=TZb1taSUAAAA:8 a=tcnv99F1KMcA:10 a=sFX2T0VcpqwA:10 a=ZUTwtFZrAAAA:8 a=r77TgQKjGQsHNAKrUKIA:9 a=9iDbn-4jx3cA:10 a=cKsnjEOsciEA:10 a=6BrDaJ5WXvREvQ-J4T4A:9 a=wPNLvfGTeEIA:10 a=Cwf1IATxPPye0MpNi3YA:9 a=IKIoO-ieCDEA:10 :: 100.00. Please check the message and try again.
Application Basics
Name Thunderbird
Version 24.6.0
User Agent Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0
Profile Folder
Show Folder
(Local drive)
Application Build ID 20140610001341
Enabled Plugins about:plugins
Build Configuration about:buildconfig
Crash Reports about:crashes
Memory Use about:memory
Mail and News Accounts
ID Incoming server Outgoing servers
Name Connection security Authentication method Name Connection security Authentication method Default?
account1 (imap) imap.secureserver.net:993 SSL passwordCleartext smtpout.secureserver.net:465 SSL passwordCleartext true
account2 (none) Local Folders plain passwordCleartext
account3 (imap) imap.secureserver.net:993 SSL passwordCleartext smtpout.secureserver.net:465 SSL passwordCleartext true
Extensions
Name Version Enabled ID
Lightning 2.6.6 true {e2fda1a4-762b-4020-b5ad-a41df1933103}
Important Modified Preferences
Name Value
accessibility.typeaheadfind.flashBar 0
browser.cache.disk.capacity 358400
browser.cache.disk.smart_size.first_run false
browser.cache.disk.smart_size.use_old_max false
browser.cache.disk.smart_size_cached_value 358400
extensions.lastAppVersion 24.6.0
font.internaluseonly.changed true
font.name.monospace.el Consolas
font.name.monospace.tr Consolas
font.name.monospace.x-baltic Consolas
font.name.monospace.x-central-euro Consolas
font.name.monospace.x-cyrillic Consolas
font.name.monospace.x-unicode Consolas
font.name.monospace.x-western Consolas
font.name.sans-serif.el Calibri
font.name.sans-serif.tr Calibri
font.name.sans-serif.x-baltic Calibri
font.name.sans-serif.x-central-euro Calibri
font.name.sans-serif.x-cyrillic Calibri
font.name.sans-serif.x-unicode Calibri
font.name.sans-serif.x-western Calibri
font.name.serif.el Cambria
font.name.serif.tr Cambria
font.name.serif.x-baltic Cambria
font.name.serif.x-central-euro Cambria
font.name.serif.x-cyrillic Cambria
font.name.serif.x-unicode Cambria
font.name.serif.x-western Cambria
font.size.fixed.el 14
font.size.fixed.tr 14
font.size.fixed.x-baltic 14
font.size.fixed.x-central-euro 14
font.size.fixed.x-cyrillic 14
font.size.fixed.x-unicode 14
font.size.fixed.x-western 14
font.size.variable.el 17
font.size.variable.tr 17
font.size.variable.x-baltic 17
font.size.variable.x-central-euro 17
font.size.variable.x-cyrillic 17
font.size.variable.x-unicode 17
font.size.variable.x-western 12
mail.openMessageBehavior.version 1
mail.winsearch.firstRunDone true
mailnews.database.global.datastore.id c88e3c64-c71c-4628-81ce-4a47013d61d
network.cookie.prefsMigrated true
places.database.lastMaintenance 1411653763
places.history.expiration.transient_current_max_pages 104858
plugin.importedState true
Graphics
Adapter Description Intel(R) HD Graphics Family
Vendor ID 0x8086
Device ID 0x0126
Adapter RAM Unknown
Adapter Drivers igdumd64 igd10umd64 igd10umd64 igdumdx32 igd10umd32 igd10umd32
Driver Version 8.15.10.2455
Driver Date 7-19-2011
Direct2D Enabled false
DirectWrite Enabled false (6.2.9200.16571)
ClearType Parameters ClearType parameters not found
WebGL Renderer false
GPU Accelerated Windows 0
AzureCanvasBackend skia
AzureFallbackCanvasBackend cairo
AzureContentBackend none
JavaScript
Incremental GC 1
Accessibility
Activated 0
Prevent Accessibility 0
Library Versions
Expected minimum version Version in use
NSPR 4.10.2 4.10.2
NSS 3.15.4 Basic ECC 3.15.4 Basic ECC
NSS Util 3.15.4 3.15.4
NSS SSL 3.15.4 Basic ECC 3.15.4 Basic ECC
NSS S/MIME 3.15.4 Basic ECC 3.15.4 Basic ECC

Answer 1

''The mail server responded:''
This is a message from the server, not Thunderbird. You'll need to talk to your email provider.
Alternatively you could encrypt the message, so that they won't be able to scan the message contents.