My Answer: Goto Email Accounts, Change the problem account, More Settings, Outgoing Server tab, and check outgoing server require authentication and choose “Log on to incoming mail server before sending mail” instead of “Use same settings as incoming” – Outlook 2007 is the first and only mail program to require any of our mail servers to use this setting. So far I’ve only confirmed the problem to be on older sendmail servers. There can be other solutions to this error message but this is one I find most often resolves it.

The Question: As a systems administrator I take calls for our tech support queue and one user called with a really odd problem. Basically it’s detailed here:

http://thepursuitofalife.com/outlook-2007-error-none-of-the-authentication-methods-supported-by-this-client-are-supported-by-your-server/

Like the above link describes the user would have to disable SMTP auth in certain locations (That’s a workaround, not the solution), even though all our servers require SMTP authentication. The above link eventually shares the true solution but it’s buried under many comments thanking the poster for the work around. So I decided to help fellow googlers by making this post.

Update: Comments about other people’s experience with this error made me want to add my further experience with it. I’ve seen this error a lot more often since I first made this post and am convinced it’s really some sort of bug with Outlook 2007. Some people cannot get rid of the error and have to continually switch between “Log on to incoming mail server before sending mail” and “Use same settings as incoming” to keep outlook sending correctly. Whereas if they switch to Windows Mail (The Vista and Windows 7 equivalent of outlook express) they never need to do anything but set ‘use same settings as incoming’ and never have any problem sending. If it’s not a ’2007 Bug’ then it’s definitely a Outlook 2007 incompatibility with certain MTAs – specifically (maybe just older) sendmail – our postfix servers don’t seem to have this bug, but like I just said only 2007 has this incompatibility so you can’t entirely blame sendmail.