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Oops. Sorry. The problem add-in is my virus checker (AVG). If I disable this,
how can I check incoming e-mails for viruses?
You don't need to scan e-mails for viruses. It is duplicate testing.
The on-access scanner will detect when there is a virus in your e-mail.
The e-mail interrogation won't detect anything that the on-access
(realtime) scanner won't detect. The same engine is used for both. If
you ever attempt to create a file from an attachment in an e-mail that
is infected then the on-access scanner will detect it. If the on-access
scanner can't detect the pest then neither will the e-mail interrogation
detect that pest. What e-mail scanning does is move forward when the
detection occurs by alerting when it is seen in the e-mail traffic
rather than later when you attempt to use the attachment. Detection
doesn't change but when the detection occurs will change.
The interrogation of the e-mail traffic by the anti-virus scanner incurs
delay. The longer the delay the more likely the e-mail client (when
receiving) or the mail host (when you send) will hit a timeout because
it doesn't see the traffic that is expected. The client issues a RETR
command to get the message from the server and expects bytes to start
showing up that constitute the message, but if there is a delay to
receive those bytes then the e-mail client errors with a timeout. When
the DATA command is sent from the e-mail client to the mail host to tell
the server to get ready for receiving the outbound message, the delay in
the interrogation can cause the server to believe that the session went
idle or timed out because it is not getting any bytes from the client
after the client gave it the DATA command to sending those bytes.
E-mail interrogation ALWAYS incurs a delay. On receiving messages, some
anti-virus programs will issue a dummy header to the e-mail client every
1 minute to keep the e-mail client from timing out while waiting for the
bytes from the mail host (through the AV proxy) to show up. Not many AV
programs do that.
E-mail interrogation is superfluous. If it works then leave it enabled
and continue onward. But if it fails or "suddenly stops working"
(usually after a program update that is automatic so the user doesn't
know the AV program just got changed) then get rid of it. If it
interferes with e-mail transmission and adds no additional level of
protection, there is no reason to keep it enabled. Some AV program let
you disable their e-mail interrogation. However, often the e-mail still
passes through their transparent proxy. The e-mail content is no longer
interrogated but if there is a problem in their proxy then there can
still remain problems. I've had AV proxies that went unresponsive so
disabling e-mail scanning didn't help because nothing was getting
through their dead proxy. A reboot might get it working again but
sometimes it required an uninstall and reinstall of the AV program.
With AVG, disabling the e-mail scanning changes the tray icon to mislead
the user to believe that something has failed in AVG. The tray icon
shouldn't change its status because you choose to no longer use one of
its functions but Grisoft believes otherwise to nag the user into
enabling e-mail scanning. Uninstall AVG and reinstall but this time do
a custom install where you deselect the e-mail scanning function.
