Customer has an odd problem with MS Outlook: some emails will not send correctly.

Incoming emails work fine, but some outgoing email will get ‘stuck’ in the outbox… then never get fully sent, yet the recipient gets multiple copies (until customer deletes the email from the outbox).

I saw this customer a few weeks earlier, with a similar problem (I disabled Trend Internet Security (TIS) from scanning outgoing emails, in order to fix the problem, but it was intermittent, so I couldn’t be sure that the problem was fixed).

I experiment a bit, and I can reproduce the problem with an email that had a 2MB attachment… it seems to be related to the attachment size, as the customer said he sent a 5MB attachment without a hitch, and smaller emails got through also.

Anyway, I’ve seen outlook do strange things before, so I thought I’d try Outlook express instead… after importing all the Outlook emails and address book, I setup the 3 email accounts, and I try sending a similar email to myself (ie with approx 2Mb attachment)

But OE also seems to struggle with the attachment. My first thought is: It can’t be the email software, as OE and outlook are actually different programs (although I’m not sure how much common code they have nowadays).

Since OE actually gives an error message (0x800CCC19) then I can google it, and then I notice a worrying trend: the error message relates to both Outlook and OE, and to problems with MANY well known antivirus and firewall software… some names mentioned are: Norton, Trend, Panda, McAfee, AVG, Zonealarm, Sygate, and many others!

I disable incoming and outgoing email scanning by trend, then restart OE, but the problem re-occurs when I send a similar email.

I then shutdown trend completely, and the previously stuck email now gets sent normally!

At this stage, since I already used up my allotted 2 hours. The customer is happy to uninstall trend, and then install antivir.

I check a few days later, and everything is working well.