Very good solution is get an anti virus that has not released years worth of poor releases. It is years I have been fielding questions from McAfee users. The McAfee release in late 2012 started the issue, and the last contact I had with McAfee on the subject was June v2013. They were apparently incapable of fixing whatever it was they had done on a permanent basis, each fix made a new problem.

If your married to McAfee, contact their support. They can fix it on an installation by installation basis, they just choose not to apparently unless you complain.

As for your assumption that anti virus software is needed for email. That is not the case. The market leader Nortons anti virus scans very little to no mail. It just pretends to. All free mail providers use SSL/TLS and now most ISPs do as well. Nortons does not scan mail from those sources. Link to the Nortons page. https://support.norton.com/sp/en/us/norton-security/current/solutions/v96137879_EndUserProfile_en_us?inid=us_hho_topnav_customersupport&q=e-mail+scanning

They make it fairly clear email scanning is not necessary, and that your covered in other areas anyway. This argument crosses anti virus programs as the same risk is being addressed.

We try an maintain what we do know here https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#Norton_Security I provide the link on the basis of we do not actually get to hear about most issues. They get resolved with the vendor or by replacing the product without any reference here. While these issues make Thunderbird look bad, there is nothing we can do to make the anti virus providers made good products, much as I would like to.

Dear Matt:

Thank you very much for your very prompt reply to my posting above dated April 15, 2015--your comments were very helpful and useful. I have since completely uninstalled the McAfee antivirus software on my computer, and since that time I have had no problems with Thunderbird locking up or becoming nonresponsive. Thus, the antivirus software was obviously the problem. The question now is: What antivirus software, if any, should I use that will have the least amount of interference with Thunderbird? Is it feasible to be protected from threats by simply using the Windows Firewall, no antivirus software at all and being very careful about not opening any attachments or links within e-mails from unknown senders? Thanks again for your assistance and for any recommendations that you may have for appropriate antivirus software.

Personally I use ESET NOD32. It is not cheap, but it is unobtrusive and appears to get the job done. Originally I was drawn there for their server protection, but since I no longer have windows servers that need is gone, but I see no reason to change.

Previously over the years I have used;

• Norton (Found it just to much embedded into the operating system. Something went wrong with it and Windows would not boot.
• Microsoft Security Essentials. Any application using large data files was unworkably slow. That included Thunderbird.
• AVG It was just clunky and I did not like it.

But the big issue these days is the products are not just anti virus, they are suites including firewalls, password managers/vaults and often spam and scam tools. It is usually these later tools that cause the most issues with the firewalls blocking anything but known versions of known software and spam tools that mess up because it has not had enough testing.

Basically your on your own in selecting a product5. I can not recommend one. But I seriously question the need for mail scanning. Especially after that remarkable admission by Symantec regarding Norton's not scanning mail.

Thunderbird does not run any scripts in mail, nor does it do anything with attachments before you open them and then it decodes them and places them in the temp folder where any good anti virus will scan them.

Personally I suggest anti virus rather than security suite software. Especially so if you use Chrome or Firefox browsers and they both use Google lists of known malware and phishing site to block inadvertent visits.

Windows has a firewall, your modem (over 90%) has one as well, those firewalls block ports, protocols and route traffic. Do you also need one that blocks programs?

Mozilla products have a password manager, do you need another? And so the list goes on.

Dear Matt:

Thank you for your very helpful comments concerning antivirus software. It certainly seems to be a minefield out there trying to balance protecting your computer systems and files, but at the same time having them operate properly. I will try an antivirus-only program and see what happens from there, and if I have anything interesting to report, I will post another comment back here in the future. Cheers!