iOS 8.1.3 emails stuck in gmail outbox

I recently found that my iPad Air is not sending mails through gmail anymore.

Receiving E-Mails and appointments through this account is no problem.

I do not have "double security" activated on the account or device, just plain vanilla.

I have several other accounts configured (Exchange Server, outlook.com, personal IMAP) each and every of them works flawlessly. Only the gmail account has this problem. It fails with the description "The connection to the outgoing server "smtp.gmail.com" failed."

Certainly I have no problems sending mail through this account using Thunderbird on Windows with identical settings, so I can definitely verify they are correct.

I tried the following procedures without luck:

• Re-enter account password
• delete Account, recreate account
• reboot device
• add alternate server for gmail with "known good" parameters as from the Apple Mail-Settings Lookup https://www.apple.com/support/mail-settings-lookup/.

It just refuses to send mails via this account. 😠

Googling this problem lists a bunch of affected users but the above procedures that did help some of them failed so far. I do not write much emails from this account so this might have been lurking a while. I might have got this while updating to any of the 8.x releases.

If I would have to guess, than probably the device fails on the SSL/TLS handshake to the SMTP server, maybe due to a certificate issue on either side, but I cannot track this down.

Any other procedures I could try other than to open a paid support call?